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9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familiarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
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90 | |
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91 | =head1 ABOUT LIBEV |
70 | |
92 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
95 | these event sources and provide your program with events. |
74 | |
96 | |
… | |
… | |
84 | =head2 FEATURES |
106 | =head2 FEATURES |
85 | |
107 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
115 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
117 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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118 | limited support for fork events (C<ev_fork>). |
96 | |
119 | |
97 | It also is quite fast (see this |
120 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
121 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
122 | for example). |
100 | |
123 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
132 | this argument. |
110 | |
133 | |
111 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
112 | |
135 | |
113 | Libev represents time as a single floating point number, representing the |
136 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
138 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
141 | any calculations on it, you should treat it as some floating point value. |
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142 | |
119 | component C<stamp> might indicate, it is also used for time differences |
143 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
121 | |
145 | |
122 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
123 | |
147 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
149 | |
173 | |
150 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
151 | |
175 | |
152 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_update_now> and C<ev_now>. |
155 | |
180 | |
156 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
157 | |
182 | |
158 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked until |
159 | either it is interrupted or the given time interval has passed. Basically |
184 | either it is interrupted or the given time interval has passed. Basically |
… | |
… | |
176 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
202 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
203 | not a problem. |
179 | |
204 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
205 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
206 | version (note, however, that this will not detect other ABI mismatches, |
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207 | such as LFS or reentrancy). |
182 | |
208 | |
183 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
212 | |
… | |
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197 | assert (("sorry, no epoll, no sex", |
223 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
224 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
225 | |
200 | =item unsigned int ev_recommended_backends () |
226 | =item unsigned int ev_recommended_backends () |
201 | |
227 | |
202 | Return the set of all backends compiled into this binary of libev and also |
228 | Return the set of all backends compiled into this binary of libev and |
203 | recommended for this platform. This set is often smaller than the one |
229 | also recommended for this platform, meaning it will work for most file |
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230 | descriptor types. This set is often smaller than the one returned by |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
231 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
232 | and will not be auto-detected unless you explicitly request it (assuming |
206 | (assuming you know what you are doing). This is the set of backends that |
233 | you know what you are doing). This is the set of backends that libev will |
207 | libev will probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
208 | |
235 | |
209 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
210 | |
237 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
238 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
213 | might be supported on the current system, you would need to look at |
240 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
243 | |
217 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
218 | |
245 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
247 | |
… | |
… | |
274 | ... |
301 | ... |
275 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
276 | |
303 | |
277 | =back |
304 | =back |
278 | |
305 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
306 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
307 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
308 | 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 |
309 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
310 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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311 | |
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312 | The library knows two types of such loops, the I<default> loop, which |
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313 | supports child process events, and dynamically created event loops which |
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314 | do not. |
284 | |
315 | |
285 | =over 4 |
316 | =over 4 |
286 | |
317 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
318 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
319 | |
289 | This will initialise the default event loop if it hasn't been initialised |
320 | 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 |
321 | 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 |
322 | 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). |
323 | C<ev_loop_new>. |
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324 | |
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325 | If the default loop is already initialised then this function simply |
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326 | returns it (and ignores the flags. If that is troubling you, check |
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327 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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328 | flags, which should almost always be C<0>, unless the caller is also the |
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329 | one calling C<ev_run> or otherwise qualifies as "the main program". |
293 | |
330 | |
294 | If you don't know what event loop to use, use the one returned from this |
331 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
332 | function (or via the C<EV_DEFAULT> macro). |
296 | |
333 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
334 | 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, |
335 | from multiple threads, you have to employ some kind of mutex (note also |
299 | as loops cannot bes hared easily between threads anyway). |
336 | that this case is unlikely, as loops cannot be shared easily between |
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337 | threads anyway). |
300 | |
338 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
339 | 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 |
340 | 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 |
341 | 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 |
342 | 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 |
343 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
306 | C<ev_default_init>. |
344 | |
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345 | Example: This is the most typical usage. |
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346 | |
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347 | if (!ev_default_loop (0)) |
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348 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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349 | |
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350 | Example: Restrict libev to the select and poll backends, and do not allow |
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351 | environment settings to be taken into account: |
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352 | |
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353 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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354 | |
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355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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356 | |
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357 | This will create and initialise a new event loop object. If the loop |
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358 | could not be initialised, returns false. |
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359 | |
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360 | Note that this function I<is> thread-safe, and one common way to use |
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361 | libev with threads is indeed to create one loop per thread, and using the |
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362 | default loop in the "main" or "initial" thread. |
307 | |
363 | |
308 | The flags argument can be used to specify special behaviour or specific |
364 | 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>). |
365 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
310 | |
366 | |
311 | The following flags are supported: |
367 | The following flags are supported: |
… | |
… | |
326 | useful to try out specific backends to test their performance, or to work |
382 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
383 | around bugs. |
328 | |
384 | |
329 | =item C<EVFLAG_FORKCHECK> |
385 | =item C<EVFLAG_FORKCHECK> |
330 | |
386 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
387 | 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 |
388 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
389 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
390 | 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 |
391 | 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 |
392 | 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 |
393 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
344 | flag. |
399 | flag. |
345 | |
400 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
401 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
402 | environment variable. |
348 | |
403 | |
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404 | =item C<EVFLAG_NOINOTIFY> |
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405 | |
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406 | When this flag is specified, then libev will not attempt to use the |
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407 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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408 | testing, this flag can be useful to conserve inotify file descriptors, as |
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409 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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410 | |
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411 | =item C<EVFLAG_SIGNALFD> |
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412 | |
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413 | When this flag is specified, then libev will attempt to use the |
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414 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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415 | delivers signals synchronously, which makes it both faster and might make |
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416 | it possible to get the queued signal data. It can also simplify signal |
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417 | handling with threads, as long as you properly block signals in your |
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418 | threads that are not interested in handling them. |
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419 | |
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420 | Signalfd will not be used by default as this changes your signal mask, and |
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421 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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422 | example) that can't properly initialise their signal masks. |
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423 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
424 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
425 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
426 | 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, |
427 | 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 |
428 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
452 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
453 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
379 | |
454 | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
455 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
456 | |
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457 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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458 | kernels). |
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459 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
460 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
461 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
462 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
463 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
464 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
466 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
467 | dropping file descriptors, requiring a system call per change per file |
|
|
468 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
469 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
470 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
471 | take considerable time (one syscall per file descriptor) and is of course |
|
|
472 | hard to detect. |
|
|
473 | |
|
|
474 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
475 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
476 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
477 | even remove them from the set) than registered in the set (especially |
|
|
478 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
479 | employing an additional generation counter and comparing that against the |
|
|
480 | events to filter out spurious ones, recreating the set when required. Last |
|
|
481 | not least, it also refuses to work with some file descriptors which work |
|
|
482 | perfectly fine with C<select> (files, many character devices...). |
389 | |
483 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
484 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
485 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
486 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
487 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
488 | file descriptors might not work very well if you register events for both |
395 | |
489 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
490 | |
400 | Best performance from this backend is achieved by not unregistering all |
491 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
492 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
493 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
494 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
495 | extra overhead. A fork can both result in spurious notifications as well |
|
|
496 | as in libev having to destroy and recreate the epoll object, which can |
|
|
497 | take considerable time and thus should be avoided. |
|
|
498 | |
|
|
499 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
500 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
501 | the usage. So sad. |
405 | |
502 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
503 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
504 | all kernel versions tested so far. |
408 | |
505 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
506 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
507 | C<EVBACKEND_POLL>. |
411 | |
508 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
509 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
510 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
511 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
512 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
513 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
514 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
515 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
516 | without API changes to existing programs. For this reason it's not being |
|
|
517 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
518 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
519 | system like NetBSD. |
420 | |
520 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
521 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
522 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
523 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
524 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
525 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
526 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
527 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
528 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
529 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
530 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
531 | cases |
431 | |
532 | |
432 | This backend usually performs well under most conditions. |
533 | This backend usually performs well under most conditions. |
433 | |
534 | |
434 | While nominally embeddable in other event loops, this doesn't work |
535 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
536 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
537 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
538 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
539 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
540 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
541 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
542 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
543 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
544 | C<NOTE_EOF>. |
444 | |
545 | |
… | |
… | |
464 | might perform better. |
565 | might perform better. |
465 | |
566 | |
466 | On the positive side, with the exception of the spurious readiness |
567 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
568 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
569 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
570 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
571 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
572 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
573 | C<EVBACKEND_POLL>. |
473 | |
574 | |
474 | =item C<EVBACKEND_ALL> |
575 | =item C<EVBACKEND_ALL> |
… | |
… | |
479 | |
580 | |
480 | It is definitely not recommended to use this flag. |
581 | It is definitely not recommended to use this flag. |
481 | |
582 | |
482 | =back |
583 | =back |
483 | |
584 | |
484 | If one or more of these are or'ed into the flags value, then only these |
585 | If one or more of the backend flags are or'ed into the flags value, |
485 | backends will be tried (in the reverse order as listed here). If none are |
586 | then only these backends will be tried (in the reverse order as listed |
486 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
587 | here). If none are specified, all backends in C<ev_recommended_backends |
487 | |
588 | ()> will be tried. |
488 | Example: This is the most typical usage. |
|
|
489 | |
|
|
490 | if (!ev_default_loop (0)) |
|
|
491 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
492 | |
|
|
493 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
494 | environment settings to be taken into account: |
|
|
495 | |
|
|
496 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
497 | |
|
|
498 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
499 | used if available (warning, breaks stuff, best use only with your own |
|
|
500 | private event loop and only if you know the OS supports your types of |
|
|
501 | fds): |
|
|
502 | |
|
|
503 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
504 | |
|
|
505 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
506 | |
|
|
507 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
508 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
509 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
510 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
511 | |
|
|
512 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
513 | libev with threads is indeed to create one loop per thread, and using the |
|
|
514 | default loop in the "main" or "initial" thread. |
|
|
515 | |
589 | |
516 | Example: Try to create a event loop that uses epoll and nothing else. |
590 | Example: Try to create a event loop that uses epoll and nothing else. |
517 | |
591 | |
518 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
592 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
519 | if (!epoller) |
593 | if (!epoller) |
520 | fatal ("no epoll found here, maybe it hides under your chair"); |
594 | fatal ("no epoll found here, maybe it hides under your chair"); |
521 | |
595 | |
|
|
596 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
597 | used if available. |
|
|
598 | |
|
|
599 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
600 | |
522 | =item ev_default_destroy () |
601 | =item ev_loop_destroy (loop) |
523 | |
602 | |
524 | Destroys the default loop again (frees all memory and kernel state |
603 | Destroys an event loop object (frees all memory and kernel state |
525 | etc.). None of the active event watchers will be stopped in the normal |
604 | etc.). None of the active event watchers will be stopped in the normal |
526 | sense, so e.g. C<ev_is_active> might still return true. It is your |
605 | sense, so e.g. C<ev_is_active> might still return true. It is your |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
606 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
607 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
608 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
609 | for example). |
531 | |
610 | |
532 | Note that certain global state, such as signal state, will not be freed by |
611 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
612 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
613 | as signal and child watchers) would need to be stopped manually. |
535 | |
614 | |
536 | In general it is not advisable to call this function except in the |
615 | This function is normally used on loop objects allocated by |
537 | rare occasion where you really need to free e.g. the signal handling |
616 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
617 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
618 | |
|
|
619 | Note that it is not advisable to call this function on the default loop |
|
|
620 | except in the rare occasion where you really need to free it's resources. |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
621 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
622 | and C<ev_loop_destroy>. |
540 | |
623 | |
541 | =item ev_loop_destroy (loop) |
624 | =item ev_loop_fork (loop) |
542 | |
625 | |
543 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
544 | earlier call to C<ev_loop_new>. |
|
|
545 | |
|
|
546 | =item ev_default_fork () |
|
|
547 | |
|
|
548 | This function sets a flag that causes subsequent C<ev_loop> iterations |
626 | This function sets a flag that causes subsequent C<ev_run> iterations to |
549 | to reinitialise the kernel state for backends that have one. Despite the |
627 | reinitialise the kernel state for backends that have one. Despite the |
550 | name, you can call it anytime, but it makes most sense after forking, in |
628 | name, you can call it anytime, but it makes most sense after forking, in |
551 | the child process (or both child and parent, but that again makes little |
629 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
552 | sense). You I<must> call it in the child before using any of the libev |
630 | child before resuming or calling C<ev_run>. |
553 | functions, and it will only take effect at the next C<ev_loop> iteration. |
631 | |
|
|
632 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
633 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
634 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
635 | during fork. |
554 | |
636 | |
555 | On the other hand, you only need to call this function in the child |
637 | On the other hand, you only need to call this function in the child |
556 | process if and only if you want to use the event library in the child. If |
638 | process if and only if you want to use the event loop in the child. If |
557 | you just fork+exec, you don't have to call it at all. |
639 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
640 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
641 | difference, but libev will usually detect this case on its own and do a |
|
|
642 | costly reset of the backend). |
558 | |
643 | |
559 | The function itself is quite fast and it's usually not a problem to call |
644 | The function itself is quite fast and it's usually not a problem to call |
560 | it just in case after a fork. To make this easy, the function will fit in |
645 | it just in case after a fork. |
561 | quite nicely into a call to C<pthread_atfork>: |
|
|
562 | |
646 | |
|
|
647 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
648 | using pthreads. |
|
|
649 | |
|
|
650 | static void |
|
|
651 | post_fork_child (void) |
|
|
652 | { |
|
|
653 | ev_loop_fork (EV_DEFAULT); |
|
|
654 | } |
|
|
655 | |
|
|
656 | ... |
563 | pthread_atfork (0, 0, ev_default_fork); |
657 | pthread_atfork (0, 0, post_fork_child); |
564 | |
|
|
565 | =item ev_loop_fork (loop) |
|
|
566 | |
|
|
567 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
568 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
569 | after fork that you want to re-use in the child, and how you do this is |
|
|
570 | entirely your own problem. |
|
|
571 | |
658 | |
572 | =item int ev_is_default_loop (loop) |
659 | =item int ev_is_default_loop (loop) |
573 | |
660 | |
574 | Returns true when the given loop is, in fact, the default loop, and false |
661 | Returns true when the given loop is, in fact, the default loop, and false |
575 | otherwise. |
662 | otherwise. |
576 | |
663 | |
577 | =item unsigned int ev_loop_count (loop) |
664 | =item unsigned int ev_iteration (loop) |
578 | |
665 | |
579 | Returns the count of loop iterations for the loop, which is identical to |
666 | Returns the current iteration count for the event loop, which is identical |
580 | the number of times libev did poll for new events. It starts at C<0> and |
667 | to the number of times libev did poll for new events. It starts at C<0> |
581 | happily wraps around with enough iterations. |
668 | and happily wraps around with enough iterations. |
582 | |
669 | |
583 | This value can sometimes be useful as a generation counter of sorts (it |
670 | This value can sometimes be useful as a generation counter of sorts (it |
584 | "ticks" the number of loop iterations), as it roughly corresponds with |
671 | "ticks" the number of loop iterations), as it roughly corresponds with |
585 | C<ev_prepare> and C<ev_check> calls. |
672 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
673 | prepare and check phases. |
|
|
674 | |
|
|
675 | =item unsigned int ev_depth (loop) |
|
|
676 | |
|
|
677 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
678 | times C<ev_run> was exited, in other words, the recursion depth. |
|
|
679 | |
|
|
680 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
681 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
682 | in which case it is higher. |
|
|
683 | |
|
|
684 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
|
|
685 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
686 | ungentleman-like behaviour unless it's really convenient. |
586 | |
687 | |
587 | =item unsigned int ev_backend (loop) |
688 | =item unsigned int ev_backend (loop) |
588 | |
689 | |
589 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
690 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
590 | use. |
691 | use. |
… | |
… | |
599 | |
700 | |
600 | =item ev_now_update (loop) |
701 | =item ev_now_update (loop) |
601 | |
702 | |
602 | Establishes the current time by querying the kernel, updating the time |
703 | Establishes the current time by querying the kernel, updating the time |
603 | returned by C<ev_now ()> in the progress. This is a costly operation and |
704 | returned by C<ev_now ()> in the progress. This is a costly operation and |
604 | is usually done automatically within C<ev_loop ()>. |
705 | is usually done automatically within C<ev_run ()>. |
605 | |
706 | |
606 | This function is rarely useful, but when some event callback runs for a |
707 | This function is rarely useful, but when some event callback runs for a |
607 | very long time without entering the event loop, updating libev's idea of |
708 | very long time without entering the event loop, updating libev's idea of |
608 | the current time is a good idea. |
709 | the current time is a good idea. |
609 | |
710 | |
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
711 | See also L<The special problem of time updates> in the C<ev_timer> section. |
611 | |
712 | |
|
|
713 | =item ev_suspend (loop) |
|
|
714 | |
|
|
715 | =item ev_resume (loop) |
|
|
716 | |
|
|
717 | These two functions suspend and resume an event loop, for use when the |
|
|
718 | loop is not used for a while and timeouts should not be processed. |
|
|
719 | |
|
|
720 | A typical use case would be an interactive program such as a game: When |
|
|
721 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
722 | would be best to handle timeouts as if no time had actually passed while |
|
|
723 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
724 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
725 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
726 | |
|
|
727 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
728 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
729 | will be rescheduled (that is, they will lose any events that would have |
|
|
730 | occurred while suspended). |
|
|
731 | |
|
|
732 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
733 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
734 | without a previous call to C<ev_suspend>. |
|
|
735 | |
|
|
736 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
737 | event loop time (see C<ev_now_update>). |
|
|
738 | |
612 | =item ev_loop (loop, int flags) |
739 | =item ev_run (loop, int flags) |
613 | |
740 | |
614 | Finally, this is it, the event handler. This function usually is called |
741 | Finally, this is it, the event handler. This function usually is called |
615 | after you initialised all your watchers and you want to start handling |
742 | after you have initialised all your watchers and you want to start |
616 | events. |
743 | handling events. It will ask the operating system for any new events, call |
|
|
744 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
745 | is why event loops are called I<loops>. |
617 | |
746 | |
618 | If the flags argument is specified as C<0>, it will not return until |
747 | If the flags argument is specified as C<0>, it will keep handling events |
619 | either no event watchers are active anymore or C<ev_unloop> was called. |
748 | until either no event watchers are active anymore or C<ev_break> was |
|
|
749 | called. |
620 | |
750 | |
621 | Please note that an explicit C<ev_unloop> is usually better than |
751 | Please note that an explicit C<ev_break> is usually better than |
622 | relying on all watchers to be stopped when deciding when a program has |
752 | relying on all watchers to be stopped when deciding when a program has |
623 | finished (especially in interactive programs), but having a program |
753 | finished (especially in interactive programs), but having a program |
624 | that automatically loops as long as it has to and no longer by virtue |
754 | that automatically loops as long as it has to and no longer by virtue |
625 | of relying on its watchers stopping correctly, that is truly a thing of |
755 | of relying on its watchers stopping correctly, that is truly a thing of |
626 | beauty. |
756 | beauty. |
627 | |
757 | |
628 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
758 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
629 | those events and any already outstanding ones, but will not block your |
759 | those events and any already outstanding ones, but will not wait and |
630 | process in case there are no events and will return after one iteration of |
760 | block your process in case there are no events and will return after one |
631 | the loop. |
761 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
762 | events while doing lengthy calculations, to keep the program responsive. |
632 | |
763 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
764 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
765 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
766 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
767 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
768 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
769 | iteration of the loop. |
639 | |
770 | |
640 | This is useful if you are waiting for some external event in conjunction |
771 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
772 | with something not expressible using other libev watchers (i.e. "roll your |
642 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
773 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
643 | usually a better approach for this kind of thing. |
774 | usually a better approach for this kind of thing. |
644 | |
775 | |
645 | Here are the gory details of what C<ev_loop> does: |
776 | Here are the gory details of what C<ev_run> does: |
646 | |
777 | |
|
|
778 | - Increment loop depth. |
|
|
779 | - Reset the ev_break status. |
647 | - Before the first iteration, call any pending watchers. |
780 | - Before the first iteration, call any pending watchers. |
|
|
781 | LOOP: |
648 | * If EVFLAG_FORKCHECK was used, check for a fork. |
782 | - If EVFLAG_FORKCHECK was used, check for a fork. |
649 | - If a fork was detected (by any means), queue and call all fork watchers. |
783 | - If a fork was detected (by any means), queue and call all fork watchers. |
650 | - Queue and call all prepare watchers. |
784 | - Queue and call all prepare watchers. |
|
|
785 | - If ev_break was called, goto FINISH. |
651 | - If we have been forked, detach and recreate the kernel state |
786 | - If we have been forked, detach and recreate the kernel state |
652 | as to not disturb the other process. |
787 | as to not disturb the other process. |
653 | - Update the kernel state with all outstanding changes. |
788 | - Update the kernel state with all outstanding changes. |
654 | - Update the "event loop time" (ev_now ()). |
789 | - Update the "event loop time" (ev_now ()). |
655 | - Calculate for how long to sleep or block, if at all |
790 | - Calculate for how long to sleep or block, if at all |
656 | (active idle watchers, EVLOOP_NONBLOCK or not having |
791 | (active idle watchers, EVRUN_NOWAIT or not having |
657 | any active watchers at all will result in not sleeping). |
792 | any active watchers at all will result in not sleeping). |
658 | - Sleep if the I/O and timer collect interval say so. |
793 | - Sleep if the I/O and timer collect interval say so. |
|
|
794 | - Increment loop iteration counter. |
659 | - Block the process, waiting for any events. |
795 | - Block the process, waiting for any events. |
660 | - Queue all outstanding I/O (fd) events. |
796 | - Queue all outstanding I/O (fd) events. |
661 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
797 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
662 | - Queue all expired timers. |
798 | - Queue all expired timers. |
663 | - Queue all expired periodics. |
799 | - Queue all expired periodics. |
664 | - Unless any events are pending now, queue all idle watchers. |
800 | - Queue all idle watchers with priority higher than that of pending events. |
665 | - Queue all check watchers. |
801 | - Queue all check watchers. |
666 | - Call all queued watchers in reverse order (i.e. check watchers first). |
802 | - Call all queued watchers in reverse order (i.e. check watchers first). |
667 | Signals and child watchers are implemented as I/O watchers, and will |
803 | Signals and child watchers are implemented as I/O watchers, and will |
668 | be handled here by queueing them when their watcher gets executed. |
804 | be handled here by queueing them when their watcher gets executed. |
669 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
805 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
670 | were used, or there are no active watchers, return, otherwise |
806 | were used, or there are no active watchers, goto FINISH, otherwise |
671 | continue with step *. |
807 | continue with step LOOP. |
|
|
808 | FINISH: |
|
|
809 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
810 | - Decrement the loop depth. |
|
|
811 | - Return. |
672 | |
812 | |
673 | Example: Queue some jobs and then loop until no events are outstanding |
813 | Example: Queue some jobs and then loop until no events are outstanding |
674 | anymore. |
814 | anymore. |
675 | |
815 | |
676 | ... queue jobs here, make sure they register event watchers as long |
816 | ... queue jobs here, make sure they register event watchers as long |
677 | ... as they still have work to do (even an idle watcher will do..) |
817 | ... as they still have work to do (even an idle watcher will do..) |
678 | ev_loop (my_loop, 0); |
818 | ev_run (my_loop, 0); |
679 | ... jobs done or somebody called unloop. yeah! |
819 | ... jobs done or somebody called unloop. yeah! |
680 | |
820 | |
681 | =item ev_unloop (loop, how) |
821 | =item ev_break (loop, how) |
682 | |
822 | |
683 | Can be used to make a call to C<ev_loop> return early (but only after it |
823 | Can be used to make a call to C<ev_run> return early (but only after it |
684 | has processed all outstanding events). The C<how> argument must be either |
824 | has processed all outstanding events). The C<how> argument must be either |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
825 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
826 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
687 | |
827 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
828 | This "unloop state" will be cleared when entering C<ev_run> again. |
689 | |
829 | |
690 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
830 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
691 | |
831 | |
692 | =item ev_ref (loop) |
832 | =item ev_ref (loop) |
693 | |
833 | |
694 | =item ev_unref (loop) |
834 | =item ev_unref (loop) |
695 | |
835 | |
696 | Ref/unref can be used to add or remove a reference count on the event |
836 | Ref/unref can be used to add or remove a reference count on the event |
697 | loop: Every watcher keeps one reference, and as long as the reference |
837 | loop: Every watcher keeps one reference, and as long as the reference |
698 | count is nonzero, C<ev_loop> will not return on its own. |
838 | count is nonzero, C<ev_run> will not return on its own. |
699 | |
839 | |
700 | If you have a watcher you never unregister that should not keep C<ev_loop> |
840 | This is useful when you have a watcher that you never intend to |
701 | from returning, call ev_unref() after starting, and ev_ref() before |
841 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
842 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
702 | stopping it. |
843 | before stopping it. |
703 | |
844 | |
704 | As an example, libev itself uses this for its internal signal pipe: It is |
845 | As an example, libev itself uses this for its internal signal pipe: It |
705 | not visible to the libev user and should not keep C<ev_loop> from exiting |
846 | is not visible to the libev user and should not keep C<ev_run> from |
706 | if no event watchers registered by it are active. It is also an excellent |
847 | exiting if no event watchers registered by it are active. It is also an |
707 | way to do this for generic recurring timers or from within third-party |
848 | excellent way to do this for generic recurring timers or from within |
708 | libraries. Just remember to I<unref after start> and I<ref before stop> |
849 | third-party libraries. Just remember to I<unref after start> and I<ref |
709 | (but only if the watcher wasn't active before, or was active before, |
850 | before stop> (but only if the watcher wasn't active before, or was active |
710 | respectively). |
851 | before, respectively. Note also that libev might stop watchers itself |
|
|
852 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
853 | in the callback). |
711 | |
854 | |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
855 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
713 | running when nothing else is active. |
856 | running when nothing else is active. |
714 | |
857 | |
715 | struct ev_signal exitsig; |
858 | ev_signal exitsig; |
716 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
859 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
717 | ev_signal_start (loop, &exitsig); |
860 | ev_signal_start (loop, &exitsig); |
718 | evf_unref (loop); |
861 | evf_unref (loop); |
719 | |
862 | |
720 | Example: For some weird reason, unregister the above signal handler again. |
863 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
744 | |
887 | |
745 | By setting a higher I<io collect interval> you allow libev to spend more |
888 | By setting a higher I<io collect interval> you allow libev to spend more |
746 | time collecting I/O events, so you can handle more events per iteration, |
889 | time collecting I/O events, so you can handle more events per iteration, |
747 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
890 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
748 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
891 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
749 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
892 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
893 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
894 | once per this interval, on average. |
750 | |
895 | |
751 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
896 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
752 | to spend more time collecting timeouts, at the expense of increased |
897 | to spend more time collecting timeouts, at the expense of increased |
753 | latency/jitter/inexactness (the watcher callback will be called |
898 | latency/jitter/inexactness (the watcher callback will be called |
754 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
899 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
756 | |
901 | |
757 | Many (busy) programs can usually benefit by setting the I/O collect |
902 | Many (busy) programs can usually benefit by setting the I/O collect |
758 | interval to a value near C<0.1> or so, which is often enough for |
903 | interval to a value near C<0.1> or so, which is often enough for |
759 | interactive servers (of course not for games), likewise for timeouts. It |
904 | interactive servers (of course not for games), likewise for timeouts. It |
760 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
905 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
761 | as this approaches the timing granularity of most systems. |
906 | as this approaches the timing granularity of most systems. Note that if |
|
|
907 | you do transactions with the outside world and you can't increase the |
|
|
908 | parallelity, then this setting will limit your transaction rate (if you |
|
|
909 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
910 | then you can't do more than 100 transactions per second). |
762 | |
911 | |
763 | Setting the I<timeout collect interval> can improve the opportunity for |
912 | Setting the I<timeout collect interval> can improve the opportunity for |
764 | saving power, as the program will "bundle" timer callback invocations that |
913 | saving power, as the program will "bundle" timer callback invocations that |
765 | are "near" in time together, by delaying some, thus reducing the number of |
914 | are "near" in time together, by delaying some, thus reducing the number of |
766 | times the process sleeps and wakes up again. Another useful technique to |
915 | times the process sleeps and wakes up again. Another useful technique to |
767 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
916 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
768 | they fire on, say, one-second boundaries only. |
917 | they fire on, say, one-second boundaries only. |
769 | |
918 | |
|
|
919 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
920 | more often than 100 times per second: |
|
|
921 | |
|
|
922 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
923 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
924 | |
|
|
925 | =item ev_invoke_pending (loop) |
|
|
926 | |
|
|
927 | This call will simply invoke all pending watchers while resetting their |
|
|
928 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
929 | but when overriding the invoke callback this call comes handy. This |
|
|
930 | function can be invoked from a watcher - this can be useful for example |
|
|
931 | when you want to do some lengthy calculation and want to pass further |
|
|
932 | event handling to another thread (you still have to make sure only one |
|
|
933 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
934 | |
|
|
935 | =item int ev_pending_count (loop) |
|
|
936 | |
|
|
937 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
938 | are pending. |
|
|
939 | |
|
|
940 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
941 | |
|
|
942 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
943 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
944 | this callback instead. This is useful, for example, when you want to |
|
|
945 | invoke the actual watchers inside another context (another thread etc.). |
|
|
946 | |
|
|
947 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
948 | callback. |
|
|
949 | |
|
|
950 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
951 | |
|
|
952 | Sometimes you want to share the same loop between multiple threads. This |
|
|
953 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
954 | each call to a libev function. |
|
|
955 | |
|
|
956 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
957 | to wait for it to return. One way around this is to wake up the event |
|
|
958 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
959 | I<release> and I<acquire> callbacks on the loop. |
|
|
960 | |
|
|
961 | When set, then C<release> will be called just before the thread is |
|
|
962 | suspended waiting for new events, and C<acquire> is called just |
|
|
963 | afterwards. |
|
|
964 | |
|
|
965 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
966 | C<acquire> will just call the mutex_lock function again. |
|
|
967 | |
|
|
968 | While event loop modifications are allowed between invocations of |
|
|
969 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
970 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
971 | have no effect on the set of file descriptors being watched, or the time |
|
|
972 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
973 | to take note of any changes you made. |
|
|
974 | |
|
|
975 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
976 | invocations of C<release> and C<acquire>. |
|
|
977 | |
|
|
978 | See also the locking example in the C<THREADS> section later in this |
|
|
979 | document. |
|
|
980 | |
|
|
981 | =item ev_set_userdata (loop, void *data) |
|
|
982 | |
|
|
983 | =item ev_userdata (loop) |
|
|
984 | |
|
|
985 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
986 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
987 | C<0.> |
|
|
988 | |
|
|
989 | These two functions can be used to associate arbitrary data with a loop, |
|
|
990 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
991 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
992 | any other purpose as well. |
|
|
993 | |
770 | =item ev_loop_verify (loop) |
994 | =item ev_verify (loop) |
771 | |
995 | |
772 | This function only does something when C<EV_VERIFY> support has been |
996 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
997 | compiled in, which is the default for non-minimal builds. It tries to go |
774 | through all internal structures and checks them for validity. If anything |
998 | through all internal structures and checks them for validity. If anything |
775 | is found to be inconsistent, it will print an error message to standard |
999 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
1000 | error and call C<abort ()>. |
777 | |
1001 | |
778 | This can be used to catch bugs inside libev itself: under normal |
1002 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
782 | =back |
1006 | =back |
783 | |
1007 | |
784 | |
1008 | |
785 | =head1 ANATOMY OF A WATCHER |
1009 | =head1 ANATOMY OF A WATCHER |
786 | |
1010 | |
|
|
1011 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1012 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1013 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1014 | |
787 | A watcher is a structure that you create and register to record your |
1015 | A watcher is an opaque structure that you allocate and register to record |
788 | interest in some event. For instance, if you want to wait for STDIN to |
1016 | your interest in some event. To make a concrete example, imagine you want |
789 | become readable, you would create an C<ev_io> watcher for that: |
1017 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1018 | for that: |
790 | |
1019 | |
791 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1020 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
792 | { |
1021 | { |
793 | ev_io_stop (w); |
1022 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
1023 | ev_break (loop, EVBREAK_ALL); |
795 | } |
1024 | } |
796 | |
1025 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
1026 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1027 | |
798 | struct ev_io stdin_watcher; |
1028 | ev_io stdin_watcher; |
|
|
1029 | |
799 | ev_init (&stdin_watcher, my_cb); |
1030 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1031 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
1032 | ev_io_start (loop, &stdin_watcher); |
|
|
1033 | |
802 | ev_loop (loop, 0); |
1034 | ev_run (loop, 0); |
803 | |
1035 | |
804 | As you can see, you are responsible for allocating the memory for your |
1036 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
1037 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
1038 | stack). |
807 | |
1039 | |
|
|
1040 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1041 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1042 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
1043 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
1044 | *, callback)>, which expects a callback to be provided. This callback is |
810 | callback gets invoked each time the event occurs (or, in the case of I/O |
1045 | invoked each time the event occurs (or, in the case of I/O watchers, each |
811 | watchers, each time the event loop detects that the file descriptor given |
1046 | time the event loop detects that the file descriptor given is readable |
812 | is readable and/or writable). |
1047 | and/or writable). |
813 | |
1048 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1049 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
1050 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1051 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
1052 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
1053 | |
819 | To make the watcher actually watch out for events, you have to start it |
1054 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1055 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
1056 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1057 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
1058 | |
824 | As long as your watcher is active (has been started but not stopped) you |
1059 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
1060 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
1061 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
1062 | |
828 | Each and every callback receives the event loop pointer as first, the |
1063 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
1064 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
1065 | third argument. |
831 | |
1066 | |
… | |
… | |
840 | =item C<EV_WRITE> |
1075 | =item C<EV_WRITE> |
841 | |
1076 | |
842 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1077 | The file descriptor in the C<ev_io> watcher has become readable and/or |
843 | writable. |
1078 | writable. |
844 | |
1079 | |
845 | =item C<EV_TIMEOUT> |
1080 | =item C<EV_TIMER> |
846 | |
1081 | |
847 | The C<ev_timer> watcher has timed out. |
1082 | The C<ev_timer> watcher has timed out. |
848 | |
1083 | |
849 | =item C<EV_PERIODIC> |
1084 | =item C<EV_PERIODIC> |
850 | |
1085 | |
… | |
… | |
868 | |
1103 | |
869 | =item C<EV_PREPARE> |
1104 | =item C<EV_PREPARE> |
870 | |
1105 | |
871 | =item C<EV_CHECK> |
1106 | =item C<EV_CHECK> |
872 | |
1107 | |
873 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1108 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
874 | to gather new events, and all C<ev_check> watchers are invoked just after |
1109 | to gather new events, and all C<ev_check> watchers are invoked just after |
875 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1110 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
876 | received events. Callbacks of both watcher types can start and stop as |
1111 | received events. Callbacks of both watcher types can start and stop as |
877 | many watchers as they want, and all of them will be taken into account |
1112 | many watchers as they want, and all of them will be taken into account |
878 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1113 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
879 | C<ev_loop> from blocking). |
1114 | C<ev_run> from blocking). |
880 | |
1115 | |
881 | =item C<EV_EMBED> |
1116 | =item C<EV_EMBED> |
882 | |
1117 | |
883 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1118 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
884 | |
1119 | |
885 | =item C<EV_FORK> |
1120 | =item C<EV_FORK> |
886 | |
1121 | |
887 | The event loop has been resumed in the child process after fork (see |
1122 | The event loop has been resumed in the child process after fork (see |
888 | C<ev_fork>). |
1123 | C<ev_fork>). |
889 | |
1124 | |
|
|
1125 | =item C<EV_CLEANUP> |
|
|
1126 | |
|
|
1127 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1128 | |
890 | =item C<EV_ASYNC> |
1129 | =item C<EV_ASYNC> |
891 | |
1130 | |
892 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1131 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1132 | |
|
|
1133 | =item C<EV_CUSTOM> |
|
|
1134 | |
|
|
1135 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1136 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
893 | |
1137 | |
894 | =item C<EV_ERROR> |
1138 | =item C<EV_ERROR> |
895 | |
1139 | |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
1140 | An unspecified error has occurred, the watcher has been stopped. This might |
897 | happen because the watcher could not be properly started because libev |
1141 | happen because the watcher could not be properly started because libev |
898 | ran out of memory, a file descriptor was found to be closed or any other |
1142 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1143 | problem. Libev considers these application bugs. |
|
|
1144 | |
899 | problem. You best act on it by reporting the problem and somehow coping |
1145 | You best act on it by reporting the problem and somehow coping with the |
900 | with the watcher being stopped. |
1146 | watcher being stopped. Note that well-written programs should not receive |
|
|
1147 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1148 | bug in your program. |
901 | |
1149 | |
902 | Libev will usually signal a few "dummy" events together with an error, for |
1150 | Libev will usually signal a few "dummy" events together with an error, for |
903 | example it might indicate that a fd is readable or writable, and if your |
1151 | example it might indicate that a fd is readable or writable, and if your |
904 | callbacks is well-written it can just attempt the operation and cope with |
1152 | callbacks is well-written it can just attempt the operation and cope with |
905 | the error from read() or write(). This will not work in multi-threaded |
1153 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
908 | |
1156 | |
909 | =back |
1157 | =back |
910 | |
1158 | |
911 | =head2 GENERIC WATCHER FUNCTIONS |
1159 | =head2 GENERIC WATCHER FUNCTIONS |
912 | |
1160 | |
913 | In the following description, C<TYPE> stands for the watcher type, |
|
|
914 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
915 | |
|
|
916 | =over 4 |
1161 | =over 4 |
917 | |
1162 | |
918 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1163 | =item C<ev_init> (ev_TYPE *watcher, callback) |
919 | |
1164 | |
920 | This macro initialises the generic portion of a watcher. The contents |
1165 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
925 | which rolls both calls into one. |
1170 | which rolls both calls into one. |
926 | |
1171 | |
927 | You can reinitialise a watcher at any time as long as it has been stopped |
1172 | You can reinitialise a watcher at any time as long as it has been stopped |
928 | (or never started) and there are no pending events outstanding. |
1173 | (or never started) and there are no pending events outstanding. |
929 | |
1174 | |
930 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1175 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
931 | int revents)>. |
1176 | int revents)>. |
932 | |
1177 | |
933 | Example: Initialise an C<ev_io> watcher in two steps. |
1178 | Example: Initialise an C<ev_io> watcher in two steps. |
934 | |
1179 | |
935 | ev_io w; |
1180 | ev_io w; |
936 | ev_init (&w, my_cb); |
1181 | ev_init (&w, my_cb); |
937 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1182 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
938 | |
1183 | |
939 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1184 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
940 | |
1185 | |
941 | This macro initialises the type-specific parts of a watcher. You need to |
1186 | This macro initialises the type-specific parts of a watcher. You need to |
942 | call C<ev_init> at least once before you call this macro, but you can |
1187 | call C<ev_init> at least once before you call this macro, but you can |
943 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1188 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
944 | macro on a watcher that is active (it can be pending, however, which is a |
1189 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
957 | |
1202 | |
958 | Example: Initialise and set an C<ev_io> watcher in one step. |
1203 | Example: Initialise and set an C<ev_io> watcher in one step. |
959 | |
1204 | |
960 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1205 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
961 | |
1206 | |
962 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1207 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
963 | |
1208 | |
964 | Starts (activates) the given watcher. Only active watchers will receive |
1209 | Starts (activates) the given watcher. Only active watchers will receive |
965 | events. If the watcher is already active nothing will happen. |
1210 | events. If the watcher is already active nothing will happen. |
966 | |
1211 | |
967 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1212 | Example: Start the C<ev_io> watcher that is being abused as example in this |
968 | whole section. |
1213 | whole section. |
969 | |
1214 | |
970 | ev_io_start (EV_DEFAULT_UC, &w); |
1215 | ev_io_start (EV_DEFAULT_UC, &w); |
971 | |
1216 | |
972 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1217 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
973 | |
1218 | |
974 | Stops the given watcher again (if active) and clears the pending |
1219 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1220 | the watcher was active or not). |
|
|
1221 | |
975 | status. It is possible that stopped watchers are pending (for example, |
1222 | It is possible that stopped watchers are pending - for example, |
976 | non-repeating timers are being stopped when they become pending), but |
1223 | non-repeating timers are being stopped when they become pending - but |
977 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1224 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
978 | you want to free or reuse the memory used by the watcher it is therefore a |
1225 | pending. If you want to free or reuse the memory used by the watcher it is |
979 | good idea to always call its C<ev_TYPE_stop> function. |
1226 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
980 | |
1227 | |
981 | =item bool ev_is_active (ev_TYPE *watcher) |
1228 | =item bool ev_is_active (ev_TYPE *watcher) |
982 | |
1229 | |
983 | Returns a true value iff the watcher is active (i.e. it has been started |
1230 | Returns a true value iff the watcher is active (i.e. it has been started |
984 | and not yet been stopped). As long as a watcher is active you must not modify |
1231 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1000 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1247 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1001 | |
1248 | |
1002 | Change the callback. You can change the callback at virtually any time |
1249 | Change the callback. You can change the callback at virtually any time |
1003 | (modulo threads). |
1250 | (modulo threads). |
1004 | |
1251 | |
1005 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1252 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1006 | |
1253 | |
1007 | =item int ev_priority (ev_TYPE *watcher) |
1254 | =item int ev_priority (ev_TYPE *watcher) |
1008 | |
1255 | |
1009 | Set and query the priority of the watcher. The priority is a small |
1256 | Set and query the priority of the watcher. The priority is a small |
1010 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1257 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1011 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1258 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1012 | before watchers with lower priority, but priority will not keep watchers |
1259 | before watchers with lower priority, but priority will not keep watchers |
1013 | from being executed (except for C<ev_idle> watchers). |
1260 | from being executed (except for C<ev_idle> watchers). |
1014 | |
1261 | |
1015 | This means that priorities are I<only> used for ordering callback |
|
|
1016 | invocation after new events have been received. This is useful, for |
|
|
1017 | example, to reduce latency after idling, or more often, to bind two |
|
|
1018 | watchers on the same event and make sure one is called first. |
|
|
1019 | |
|
|
1020 | If you need to suppress invocation when higher priority events are pending |
1262 | If you need to suppress invocation when higher priority events are pending |
1021 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1263 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1022 | |
1264 | |
1023 | You I<must not> change the priority of a watcher as long as it is active or |
1265 | You I<must not> change the priority of a watcher as long as it is active or |
1024 | pending. |
1266 | pending. |
1025 | |
1267 | |
|
|
1268 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1269 | fine, as long as you do not mind that the priority value you query might |
|
|
1270 | or might not have been clamped to the valid range. |
|
|
1271 | |
1026 | The default priority used by watchers when no priority has been set is |
1272 | The default priority used by watchers when no priority has been set is |
1027 | always C<0>, which is supposed to not be too high and not be too low :). |
1273 | always C<0>, which is supposed to not be too high and not be too low :). |
1028 | |
1274 | |
1029 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1275 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1030 | fine, as long as you do not mind that the priority value you query might |
1276 | priorities. |
1031 | or might not have been adjusted to be within valid range. |
|
|
1032 | |
1277 | |
1033 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1278 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1034 | |
1279 | |
1035 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1280 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1036 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1281 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1044 | watcher isn't pending it does nothing and returns C<0>. |
1289 | watcher isn't pending it does nothing and returns C<0>. |
1045 | |
1290 | |
1046 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1291 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1047 | callback to be invoked, which can be accomplished with this function. |
1292 | callback to be invoked, which can be accomplished with this function. |
1048 | |
1293 | |
|
|
1294 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1295 | |
|
|
1296 | Feeds the given event set into the event loop, as if the specified event |
|
|
1297 | had happened for the specified watcher (which must be a pointer to an |
|
|
1298 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1299 | not free the watcher as long as it has pending events. |
|
|
1300 | |
|
|
1301 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1302 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1303 | not started in the first place. |
|
|
1304 | |
|
|
1305 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1306 | functions that do not need a watcher. |
|
|
1307 | |
1049 | =back |
1308 | =back |
1050 | |
|
|
1051 | |
1309 | |
1052 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1310 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1053 | |
1311 | |
1054 | Each watcher has, by default, a member C<void *data> that you can change |
1312 | Each watcher has, by default, a member C<void *data> that you can change |
1055 | and read at any time: libev will completely ignore it. This can be used |
1313 | and read at any time: libev will completely ignore it. This can be used |
… | |
… | |
1058 | member, you can also "subclass" the watcher type and provide your own |
1316 | member, you can also "subclass" the watcher type and provide your own |
1059 | data: |
1317 | data: |
1060 | |
1318 | |
1061 | struct my_io |
1319 | struct my_io |
1062 | { |
1320 | { |
1063 | struct ev_io io; |
1321 | ev_io io; |
1064 | int otherfd; |
1322 | int otherfd; |
1065 | void *somedata; |
1323 | void *somedata; |
1066 | struct whatever *mostinteresting; |
1324 | struct whatever *mostinteresting; |
1067 | }; |
1325 | }; |
1068 | |
1326 | |
… | |
… | |
1071 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1329 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1072 | |
1330 | |
1073 | And since your callback will be called with a pointer to the watcher, you |
1331 | And since your callback will be called with a pointer to the watcher, you |
1074 | can cast it back to your own type: |
1332 | can cast it back to your own type: |
1075 | |
1333 | |
1076 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1334 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1077 | { |
1335 | { |
1078 | struct my_io *w = (struct my_io *)w_; |
1336 | struct my_io *w = (struct my_io *)w_; |
1079 | ... |
1337 | ... |
1080 | } |
1338 | } |
1081 | |
1339 | |
… | |
… | |
1099 | programmers): |
1357 | programmers): |
1100 | |
1358 | |
1101 | #include <stddef.h> |
1359 | #include <stddef.h> |
1102 | |
1360 | |
1103 | static void |
1361 | static void |
1104 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1362 | t1_cb (EV_P_ ev_timer *w, int revents) |
1105 | { |
1363 | { |
1106 | struct my_biggy big = (struct my_biggy * |
1364 | struct my_biggy big = (struct my_biggy *) |
1107 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1365 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1108 | } |
1366 | } |
1109 | |
1367 | |
1110 | static void |
1368 | static void |
1111 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1369 | t2_cb (EV_P_ ev_timer *w, int revents) |
1112 | { |
1370 | { |
1113 | struct my_biggy big = (struct my_biggy * |
1371 | struct my_biggy big = (struct my_biggy *) |
1114 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1372 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1115 | } |
1373 | } |
|
|
1374 | |
|
|
1375 | =head2 WATCHER STATES |
|
|
1376 | |
|
|
1377 | There are various watcher states mentioned throughout this manual - |
|
|
1378 | active, pending and so on. In this section these states and the rules to |
|
|
1379 | transition between them will be described in more detail - and while these |
|
|
1380 | rules might look complicated, they usually do "the right thing". |
|
|
1381 | |
|
|
1382 | =over 4 |
|
|
1383 | |
|
|
1384 | =item initialiased |
|
|
1385 | |
|
|
1386 | Before a watcher can be registered with the event looop it has to be |
|
|
1387 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1388 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1389 | |
|
|
1390 | In this state it is simply some block of memory that is suitable for use |
|
|
1391 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1392 | |
|
|
1393 | =item started/running/active |
|
|
1394 | |
|
|
1395 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1396 | property of the event loop, and is actively waiting for events. While in |
|
|
1397 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1398 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1399 | and call libev functions on it that are documented to work on active watchers. |
|
|
1400 | |
|
|
1401 | =item pending |
|
|
1402 | |
|
|
1403 | If a watcher is active and libev determines that an event it is interested |
|
|
1404 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1405 | stay in this pending state until either it is stopped or its callback is |
|
|
1406 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1407 | callback. |
|
|
1408 | |
|
|
1409 | The watcher might or might not be active while it is pending (for example, |
|
|
1410 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1411 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1412 | but it is still property of the event loop at this time, so cannot be |
|
|
1413 | moved, freed or reused. And if it is active the rules described in the |
|
|
1414 | previous item still apply. |
|
|
1415 | |
|
|
1416 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1417 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1418 | active. |
|
|
1419 | |
|
|
1420 | =item stopped |
|
|
1421 | |
|
|
1422 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1423 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1424 | latter will clear any pending state the watcher might be in, regardless |
|
|
1425 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1426 | freeing it is often a good idea. |
|
|
1427 | |
|
|
1428 | While stopped (and not pending) the watcher is essentially in the |
|
|
1429 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1430 | you wish. |
|
|
1431 | |
|
|
1432 | =back |
|
|
1433 | |
|
|
1434 | =head2 WATCHER PRIORITY MODELS |
|
|
1435 | |
|
|
1436 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1437 | integers that influence the ordering of event callback invocation |
|
|
1438 | between watchers in some way, all else being equal. |
|
|
1439 | |
|
|
1440 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1441 | description for the more technical details such as the actual priority |
|
|
1442 | range. |
|
|
1443 | |
|
|
1444 | There are two common ways how these these priorities are being interpreted |
|
|
1445 | by event loops: |
|
|
1446 | |
|
|
1447 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1448 | of lower priority watchers, which means as long as higher priority |
|
|
1449 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1450 | |
|
|
1451 | The less common only-for-ordering model uses priorities solely to order |
|
|
1452 | callback invocation within a single event loop iteration: Higher priority |
|
|
1453 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1454 | before polling for new events. |
|
|
1455 | |
|
|
1456 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1457 | except for idle watchers (which use the lock-out model). |
|
|
1458 | |
|
|
1459 | The rationale behind this is that implementing the lock-out model for |
|
|
1460 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1461 | libraries will just poll for the same events again and again as long as |
|
|
1462 | their callbacks have not been executed, which is very inefficient in the |
|
|
1463 | common case of one high-priority watcher locking out a mass of lower |
|
|
1464 | priority ones. |
|
|
1465 | |
|
|
1466 | Static (ordering) priorities are most useful when you have two or more |
|
|
1467 | watchers handling the same resource: a typical usage example is having an |
|
|
1468 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1469 | timeouts. Under load, data might be received while the program handles |
|
|
1470 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1471 | handler will be executed before checking for data. In that case, giving |
|
|
1472 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1473 | handled first even under adverse conditions (which is usually, but not |
|
|
1474 | always, what you want). |
|
|
1475 | |
|
|
1476 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1477 | will only be executed when no same or higher priority watchers have |
|
|
1478 | received events, they can be used to implement the "lock-out" model when |
|
|
1479 | required. |
|
|
1480 | |
|
|
1481 | For example, to emulate how many other event libraries handle priorities, |
|
|
1482 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1483 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1484 | processing is done in the idle watcher callback. This causes libev to |
|
|
1485 | continuously poll and process kernel event data for the watcher, but when |
|
|
1486 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1487 | workable. |
|
|
1488 | |
|
|
1489 | Usually, however, the lock-out model implemented that way will perform |
|
|
1490 | miserably under the type of load it was designed to handle. In that case, |
|
|
1491 | it might be preferable to stop the real watcher before starting the |
|
|
1492 | idle watcher, so the kernel will not have to process the event in case |
|
|
1493 | the actual processing will be delayed for considerable time. |
|
|
1494 | |
|
|
1495 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1496 | priority than the default, and which should only process data when no |
|
|
1497 | other events are pending: |
|
|
1498 | |
|
|
1499 | ev_idle idle; // actual processing watcher |
|
|
1500 | ev_io io; // actual event watcher |
|
|
1501 | |
|
|
1502 | static void |
|
|
1503 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1504 | { |
|
|
1505 | // stop the I/O watcher, we received the event, but |
|
|
1506 | // are not yet ready to handle it. |
|
|
1507 | ev_io_stop (EV_A_ w); |
|
|
1508 | |
|
|
1509 | // start the idle watcher to handle the actual event. |
|
|
1510 | // it will not be executed as long as other watchers |
|
|
1511 | // with the default priority are receiving events. |
|
|
1512 | ev_idle_start (EV_A_ &idle); |
|
|
1513 | } |
|
|
1514 | |
|
|
1515 | static void |
|
|
1516 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1517 | { |
|
|
1518 | // actual processing |
|
|
1519 | read (STDIN_FILENO, ...); |
|
|
1520 | |
|
|
1521 | // have to start the I/O watcher again, as |
|
|
1522 | // we have handled the event |
|
|
1523 | ev_io_start (EV_P_ &io); |
|
|
1524 | } |
|
|
1525 | |
|
|
1526 | // initialisation |
|
|
1527 | ev_idle_init (&idle, idle_cb); |
|
|
1528 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1529 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1530 | |
|
|
1531 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1532 | low-priority connections can not be locked out forever under load. This |
|
|
1533 | enables your program to keep a lower latency for important connections |
|
|
1534 | during short periods of high load, while not completely locking out less |
|
|
1535 | important ones. |
1116 | |
1536 | |
1117 | |
1537 | |
1118 | =head1 WATCHER TYPES |
1538 | =head1 WATCHER TYPES |
1119 | |
1539 | |
1120 | This section describes each watcher in detail, but will not repeat |
1540 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1146 | descriptors to non-blocking mode is also usually a good idea (but not |
1566 | descriptors to non-blocking mode is also usually a good idea (but not |
1147 | required if you know what you are doing). |
1567 | required if you know what you are doing). |
1148 | |
1568 | |
1149 | If you cannot use non-blocking mode, then force the use of a |
1569 | If you cannot use non-blocking mode, then force the use of a |
1150 | known-to-be-good backend (at the time of this writing, this includes only |
1570 | known-to-be-good backend (at the time of this writing, this includes only |
1151 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1571 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1572 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1573 | files) - libev doesn't guarantee any specific behaviour in that case. |
1152 | |
1574 | |
1153 | Another thing you have to watch out for is that it is quite easy to |
1575 | Another thing you have to watch out for is that it is quite easy to |
1154 | receive "spurious" readiness notifications, that is your callback might |
1576 | receive "spurious" readiness notifications, that is your callback might |
1155 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1577 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1156 | because there is no data. Not only are some backends known to create a |
1578 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1221 | |
1643 | |
1222 | So when you encounter spurious, unexplained daemon exits, make sure you |
1644 | So when you encounter spurious, unexplained daemon exits, make sure you |
1223 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1645 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1224 | somewhere, as that would have given you a big clue). |
1646 | somewhere, as that would have given you a big clue). |
1225 | |
1647 | |
|
|
1648 | =head3 The special problem of accept()ing when you can't |
|
|
1649 | |
|
|
1650 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1651 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1652 | connection from the pending queue in all error cases. |
|
|
1653 | |
|
|
1654 | For example, larger servers often run out of file descriptors (because |
|
|
1655 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1656 | rejecting the connection, leading to libev signalling readiness on |
|
|
1657 | the next iteration again (the connection still exists after all), and |
|
|
1658 | typically causing the program to loop at 100% CPU usage. |
|
|
1659 | |
|
|
1660 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1661 | operating systems, there is usually little the app can do to remedy the |
|
|
1662 | situation, and no known thread-safe method of removing the connection to |
|
|
1663 | cope with overload is known (to me). |
|
|
1664 | |
|
|
1665 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1666 | - when the program encounters an overload, it will just loop until the |
|
|
1667 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1668 | event-based way to handle this situation, so it's the best one can do. |
|
|
1669 | |
|
|
1670 | A better way to handle the situation is to log any errors other than |
|
|
1671 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1672 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1673 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1674 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1675 | usage. |
|
|
1676 | |
|
|
1677 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1678 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1679 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1680 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1681 | clients under typical overload conditions. |
|
|
1682 | |
|
|
1683 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1684 | is often done with C<malloc> failures, but this results in an easy |
|
|
1685 | opportunity for a DoS attack. |
1226 | |
1686 | |
1227 | =head3 Watcher-Specific Functions |
1687 | =head3 Watcher-Specific Functions |
1228 | |
1688 | |
1229 | =over 4 |
1689 | =over 4 |
1230 | |
1690 | |
… | |
… | |
1251 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1711 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1252 | readable, but only once. Since it is likely line-buffered, you could |
1712 | readable, but only once. Since it is likely line-buffered, you could |
1253 | attempt to read a whole line in the callback. |
1713 | attempt to read a whole line in the callback. |
1254 | |
1714 | |
1255 | static void |
1715 | static void |
1256 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1716 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1257 | { |
1717 | { |
1258 | ev_io_stop (loop, w); |
1718 | ev_io_stop (loop, w); |
1259 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1719 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1260 | } |
1720 | } |
1261 | |
1721 | |
1262 | ... |
1722 | ... |
1263 | struct ev_loop *loop = ev_default_init (0); |
1723 | struct ev_loop *loop = ev_default_init (0); |
1264 | struct ev_io stdin_readable; |
1724 | ev_io stdin_readable; |
1265 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1725 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1266 | ev_io_start (loop, &stdin_readable); |
1726 | ev_io_start (loop, &stdin_readable); |
1267 | ev_loop (loop, 0); |
1727 | ev_run (loop, 0); |
1268 | |
1728 | |
1269 | |
1729 | |
1270 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1730 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1271 | |
1731 | |
1272 | Timer watchers are simple relative timers that generate an event after a |
1732 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1277 | year, it will still time out after (roughly) one hour. "Roughly" because |
1737 | year, it will still time out after (roughly) one hour. "Roughly" because |
1278 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1738 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1279 | monotonic clock option helps a lot here). |
1739 | monotonic clock option helps a lot here). |
1280 | |
1740 | |
1281 | The callback is guaranteed to be invoked only I<after> its timeout has |
1741 | The callback is guaranteed to be invoked only I<after> its timeout has |
1282 | passed, but if multiple timers become ready during the same loop iteration |
1742 | passed (not I<at>, so on systems with very low-resolution clocks this |
1283 | then order of execution is undefined. |
1743 | might introduce a small delay). If multiple timers become ready during the |
|
|
1744 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1745 | before ones of the same priority with later time-out values (but this is |
|
|
1746 | no longer true when a callback calls C<ev_run> recursively). |
|
|
1747 | |
|
|
1748 | =head3 Be smart about timeouts |
|
|
1749 | |
|
|
1750 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1751 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1752 | you want to raise some error after a while. |
|
|
1753 | |
|
|
1754 | What follows are some ways to handle this problem, from obvious and |
|
|
1755 | inefficient to smart and efficient. |
|
|
1756 | |
|
|
1757 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1758 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1759 | data or other life sign was received). |
|
|
1760 | |
|
|
1761 | =over 4 |
|
|
1762 | |
|
|
1763 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1764 | |
|
|
1765 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1766 | start the watcher: |
|
|
1767 | |
|
|
1768 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1769 | ev_timer_start (loop, timer); |
|
|
1770 | |
|
|
1771 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1772 | and start it again: |
|
|
1773 | |
|
|
1774 | ev_timer_stop (loop, timer); |
|
|
1775 | ev_timer_set (timer, 60., 0.); |
|
|
1776 | ev_timer_start (loop, timer); |
|
|
1777 | |
|
|
1778 | This is relatively simple to implement, but means that each time there is |
|
|
1779 | some activity, libev will first have to remove the timer from its internal |
|
|
1780 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1781 | still not a constant-time operation. |
|
|
1782 | |
|
|
1783 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1784 | |
|
|
1785 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1786 | C<ev_timer_start>. |
|
|
1787 | |
|
|
1788 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1789 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1790 | successfully read or write some data. If you go into an idle state where |
|
|
1791 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1792 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1793 | |
|
|
1794 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1795 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1796 | member and C<ev_timer_again>. |
|
|
1797 | |
|
|
1798 | At start: |
|
|
1799 | |
|
|
1800 | ev_init (timer, callback); |
|
|
1801 | timer->repeat = 60.; |
|
|
1802 | ev_timer_again (loop, timer); |
|
|
1803 | |
|
|
1804 | Each time there is some activity: |
|
|
1805 | |
|
|
1806 | ev_timer_again (loop, timer); |
|
|
1807 | |
|
|
1808 | It is even possible to change the time-out on the fly, regardless of |
|
|
1809 | whether the watcher is active or not: |
|
|
1810 | |
|
|
1811 | timer->repeat = 30.; |
|
|
1812 | ev_timer_again (loop, timer); |
|
|
1813 | |
|
|
1814 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1815 | you want to modify its timeout value, as libev does not have to completely |
|
|
1816 | remove and re-insert the timer from/into its internal data structure. |
|
|
1817 | |
|
|
1818 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1819 | |
|
|
1820 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1821 | |
|
|
1822 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1823 | relatively long compared to the intervals between other activity - in |
|
|
1824 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1825 | associated activity resets. |
|
|
1826 | |
|
|
1827 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1828 | but remember the time of last activity, and check for a real timeout only |
|
|
1829 | within the callback: |
|
|
1830 | |
|
|
1831 | ev_tstamp last_activity; // time of last activity |
|
|
1832 | |
|
|
1833 | static void |
|
|
1834 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1835 | { |
|
|
1836 | ev_tstamp now = ev_now (EV_A); |
|
|
1837 | ev_tstamp timeout = last_activity + 60.; |
|
|
1838 | |
|
|
1839 | // if last_activity + 60. is older than now, we did time out |
|
|
1840 | if (timeout < now) |
|
|
1841 | { |
|
|
1842 | // timeout occurred, take action |
|
|
1843 | } |
|
|
1844 | else |
|
|
1845 | { |
|
|
1846 | // callback was invoked, but there was some activity, re-arm |
|
|
1847 | // the watcher to fire in last_activity + 60, which is |
|
|
1848 | // guaranteed to be in the future, so "again" is positive: |
|
|
1849 | w->repeat = timeout - now; |
|
|
1850 | ev_timer_again (EV_A_ w); |
|
|
1851 | } |
|
|
1852 | } |
|
|
1853 | |
|
|
1854 | To summarise the callback: first calculate the real timeout (defined |
|
|
1855 | as "60 seconds after the last activity"), then check if that time has |
|
|
1856 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1857 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1858 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1859 | a timeout then. |
|
|
1860 | |
|
|
1861 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1862 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1863 | |
|
|
1864 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1865 | minus half the average time between activity), but virtually no calls to |
|
|
1866 | libev to change the timeout. |
|
|
1867 | |
|
|
1868 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1869 | to the current time (meaning we just have some activity :), then call the |
|
|
1870 | callback, which will "do the right thing" and start the timer: |
|
|
1871 | |
|
|
1872 | ev_init (timer, callback); |
|
|
1873 | last_activity = ev_now (loop); |
|
|
1874 | callback (loop, timer, EV_TIMER); |
|
|
1875 | |
|
|
1876 | And when there is some activity, simply store the current time in |
|
|
1877 | C<last_activity>, no libev calls at all: |
|
|
1878 | |
|
|
1879 | last_activity = ev_now (loop); |
|
|
1880 | |
|
|
1881 | This technique is slightly more complex, but in most cases where the |
|
|
1882 | time-out is unlikely to be triggered, much more efficient. |
|
|
1883 | |
|
|
1884 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1885 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1886 | fix things for you. |
|
|
1887 | |
|
|
1888 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1889 | |
|
|
1890 | If there is not one request, but many thousands (millions...), all |
|
|
1891 | employing some kind of timeout with the same timeout value, then one can |
|
|
1892 | do even better: |
|
|
1893 | |
|
|
1894 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1895 | at the I<end> of the list. |
|
|
1896 | |
|
|
1897 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1898 | the list is expected to fire (for example, using the technique #3). |
|
|
1899 | |
|
|
1900 | When there is some activity, remove the timer from the list, recalculate |
|
|
1901 | the timeout, append it to the end of the list again, and make sure to |
|
|
1902 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1903 | |
|
|
1904 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1905 | starting, stopping and updating the timers, at the expense of a major |
|
|
1906 | complication, and having to use a constant timeout. The constant timeout |
|
|
1907 | ensures that the list stays sorted. |
|
|
1908 | |
|
|
1909 | =back |
|
|
1910 | |
|
|
1911 | So which method the best? |
|
|
1912 | |
|
|
1913 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1914 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1915 | better, and isn't very complicated either. In most case, choosing either |
|
|
1916 | one is fine, with #3 being better in typical situations. |
|
|
1917 | |
|
|
1918 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1919 | rather complicated, but extremely efficient, something that really pays |
|
|
1920 | off after the first million or so of active timers, i.e. it's usually |
|
|
1921 | overkill :) |
1284 | |
1922 | |
1285 | =head3 The special problem of time updates |
1923 | =head3 The special problem of time updates |
1286 | |
1924 | |
1287 | Establishing the current time is a costly operation (it usually takes at |
1925 | Establishing the current time is a costly operation (it usually takes at |
1288 | least two system calls): EV therefore updates its idea of the current |
1926 | least two system calls): EV therefore updates its idea of the current |
1289 | time only before and after C<ev_loop> collects new events, which causes a |
1927 | time only before and after C<ev_run> collects new events, which causes a |
1290 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1928 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1291 | lots of events in one iteration. |
1929 | lots of events in one iteration. |
1292 | |
1930 | |
1293 | The relative timeouts are calculated relative to the C<ev_now ()> |
1931 | The relative timeouts are calculated relative to the C<ev_now ()> |
1294 | time. This is usually the right thing as this timestamp refers to the time |
1932 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1300 | |
1938 | |
1301 | If the event loop is suspended for a long time, you can also force an |
1939 | If the event loop is suspended for a long time, you can also force an |
1302 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1940 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1303 | ()>. |
1941 | ()>. |
1304 | |
1942 | |
|
|
1943 | =head3 The special problems of suspended animation |
|
|
1944 | |
|
|
1945 | When you leave the server world it is quite customary to hit machines that |
|
|
1946 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1947 | |
|
|
1948 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1949 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1950 | to run until the system is suspended, but they will not advance while the |
|
|
1951 | system is suspended. That means, on resume, it will be as if the program |
|
|
1952 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1953 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1954 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1955 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1956 | be adjusted accordingly. |
|
|
1957 | |
|
|
1958 | I would not be surprised to see different behaviour in different between |
|
|
1959 | operating systems, OS versions or even different hardware. |
|
|
1960 | |
|
|
1961 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1962 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1963 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1964 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1965 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1966 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1967 | |
|
|
1968 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1969 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1970 | deterministic behaviour in this case (you can do nothing against |
|
|
1971 | C<SIGSTOP>). |
|
|
1972 | |
1305 | =head3 Watcher-Specific Functions and Data Members |
1973 | =head3 Watcher-Specific Functions and Data Members |
1306 | |
1974 | |
1307 | =over 4 |
1975 | =over 4 |
1308 | |
1976 | |
1309 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1977 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1332 | If the timer is started but non-repeating, stop it (as if it timed out). |
2000 | If the timer is started but non-repeating, stop it (as if it timed out). |
1333 | |
2001 | |
1334 | If the timer is repeating, either start it if necessary (with the |
2002 | If the timer is repeating, either start it if necessary (with the |
1335 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2003 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1336 | |
2004 | |
1337 | This sounds a bit complicated, but here is a useful and typical |
2005 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1338 | example: Imagine you have a TCP connection and you want a so-called idle |
2006 | usage example. |
1339 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1340 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1341 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1342 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1343 | you go into an idle state where you do not expect data to travel on the |
|
|
1344 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1345 | automatically restart it if need be. |
|
|
1346 | |
2007 | |
1347 | That means you can ignore the C<after> value and C<ev_timer_start> |
2008 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1348 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1349 | |
2009 | |
1350 | ev_timer_init (timer, callback, 0., 5.); |
2010 | Returns the remaining time until a timer fires. If the timer is active, |
1351 | ev_timer_again (loop, timer); |
2011 | then this time is relative to the current event loop time, otherwise it's |
1352 | ... |
2012 | the timeout value currently configured. |
1353 | timer->again = 17.; |
|
|
1354 | ev_timer_again (loop, timer); |
|
|
1355 | ... |
|
|
1356 | timer->again = 10.; |
|
|
1357 | ev_timer_again (loop, timer); |
|
|
1358 | |
2013 | |
1359 | This is more slightly efficient then stopping/starting the timer each time |
2014 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1360 | you want to modify its timeout value. |
2015 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1361 | |
2016 | will return C<4>. When the timer expires and is restarted, it will return |
1362 | Note, however, that it is often even more efficient to remember the |
2017 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1363 | time of the last activity and let the timer time-out naturally. In the |
2018 | too), and so on. |
1364 | callback, you then check whether the time-out is real, or, if there was |
|
|
1365 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1366 | timeout - ev_now ()" seconds. |
|
|
1367 | |
2019 | |
1368 | =item ev_tstamp repeat [read-write] |
2020 | =item ev_tstamp repeat [read-write] |
1369 | |
2021 | |
1370 | The current C<repeat> value. Will be used each time the watcher times out |
2022 | The current C<repeat> value. Will be used each time the watcher times out |
1371 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2023 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1376 | =head3 Examples |
2028 | =head3 Examples |
1377 | |
2029 | |
1378 | Example: Create a timer that fires after 60 seconds. |
2030 | Example: Create a timer that fires after 60 seconds. |
1379 | |
2031 | |
1380 | static void |
2032 | static void |
1381 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2033 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1382 | { |
2034 | { |
1383 | .. one minute over, w is actually stopped right here |
2035 | .. one minute over, w is actually stopped right here |
1384 | } |
2036 | } |
1385 | |
2037 | |
1386 | struct ev_timer mytimer; |
2038 | ev_timer mytimer; |
1387 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2039 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1388 | ev_timer_start (loop, &mytimer); |
2040 | ev_timer_start (loop, &mytimer); |
1389 | |
2041 | |
1390 | Example: Create a timeout timer that times out after 10 seconds of |
2042 | Example: Create a timeout timer that times out after 10 seconds of |
1391 | inactivity. |
2043 | inactivity. |
1392 | |
2044 | |
1393 | static void |
2045 | static void |
1394 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2046 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1395 | { |
2047 | { |
1396 | .. ten seconds without any activity |
2048 | .. ten seconds without any activity |
1397 | } |
2049 | } |
1398 | |
2050 | |
1399 | struct ev_timer mytimer; |
2051 | ev_timer mytimer; |
1400 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2052 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1401 | ev_timer_again (&mytimer); /* start timer */ |
2053 | ev_timer_again (&mytimer); /* start timer */ |
1402 | ev_loop (loop, 0); |
2054 | ev_run (loop, 0); |
1403 | |
2055 | |
1404 | // and in some piece of code that gets executed on any "activity": |
2056 | // and in some piece of code that gets executed on any "activity": |
1405 | // reset the timeout to start ticking again at 10 seconds |
2057 | // reset the timeout to start ticking again at 10 seconds |
1406 | ev_timer_again (&mytimer); |
2058 | ev_timer_again (&mytimer); |
1407 | |
2059 | |
… | |
… | |
1409 | =head2 C<ev_periodic> - to cron or not to cron? |
2061 | =head2 C<ev_periodic> - to cron or not to cron? |
1410 | |
2062 | |
1411 | Periodic watchers are also timers of a kind, but they are very versatile |
2063 | Periodic watchers are also timers of a kind, but they are very versatile |
1412 | (and unfortunately a bit complex). |
2064 | (and unfortunately a bit complex). |
1413 | |
2065 | |
1414 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2066 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1415 | but on wall clock time (absolute time). You can tell a periodic watcher |
2067 | relative time, the physical time that passes) but on wall clock time |
1416 | to trigger after some specific point in time. For example, if you tell a |
2068 | (absolute time, the thing you can read on your calender or clock). The |
1417 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2069 | difference is that wall clock time can run faster or slower than real |
1418 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2070 | time, and time jumps are not uncommon (e.g. when you adjust your |
1419 | clock to January of the previous year, then it will take more than year |
2071 | wrist-watch). |
1420 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1421 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1422 | |
2072 | |
|
|
2073 | You can tell a periodic watcher to trigger after some specific point |
|
|
2074 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2075 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2076 | not a delay) and then reset your system clock to January of the previous |
|
|
2077 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2078 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2079 | it, as it uses a relative timeout). |
|
|
2080 | |
1423 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2081 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1424 | such as triggering an event on each "midnight, local time", or other |
2082 | timers, such as triggering an event on each "midnight, local time", or |
1425 | complicated rules. |
2083 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2084 | those cannot react to time jumps. |
1426 | |
2085 | |
1427 | As with timers, the callback is guaranteed to be invoked only when the |
2086 | As with timers, the callback is guaranteed to be invoked only when the |
1428 | time (C<at>) has passed, but if multiple periodic timers become ready |
2087 | point in time where it is supposed to trigger has passed. If multiple |
1429 | during the same loop iteration, then order of execution is undefined. |
2088 | timers become ready during the same loop iteration then the ones with |
|
|
2089 | earlier time-out values are invoked before ones with later time-out values |
|
|
2090 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1430 | |
2091 | |
1431 | =head3 Watcher-Specific Functions and Data Members |
2092 | =head3 Watcher-Specific Functions and Data Members |
1432 | |
2093 | |
1433 | =over 4 |
2094 | =over 4 |
1434 | |
2095 | |
1435 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2096 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1436 | |
2097 | |
1437 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2098 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1438 | |
2099 | |
1439 | Lots of arguments, lets sort it out... There are basically three modes of |
2100 | Lots of arguments, let's sort it out... There are basically three modes of |
1440 | operation, and we will explain them from simplest to most complex: |
2101 | operation, and we will explain them from simplest to most complex: |
1441 | |
2102 | |
1442 | =over 4 |
2103 | =over 4 |
1443 | |
2104 | |
1444 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2105 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1445 | |
2106 | |
1446 | In this configuration the watcher triggers an event after the wall clock |
2107 | In this configuration the watcher triggers an event after the wall clock |
1447 | time C<at> has passed. It will not repeat and will not adjust when a time |
2108 | time C<offset> has passed. It will not repeat and will not adjust when a |
1448 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2109 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1449 | only run when the system clock reaches or surpasses this time. |
2110 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2111 | this point in time. |
1450 | |
2112 | |
1451 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2113 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1452 | |
2114 | |
1453 | In this mode the watcher will always be scheduled to time out at the next |
2115 | In this mode the watcher will always be scheduled to time out at the next |
1454 | C<at + N * interval> time (for some integer N, which can also be negative) |
2116 | C<offset + N * interval> time (for some integer N, which can also be |
1455 | and then repeat, regardless of any time jumps. |
2117 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2118 | argument is merely an offset into the C<interval> periods. |
1456 | |
2119 | |
1457 | This can be used to create timers that do not drift with respect to the |
2120 | This can be used to create timers that do not drift with respect to the |
1458 | system clock, for example, here is a C<ev_periodic> that triggers each |
2121 | system clock, for example, here is an C<ev_periodic> that triggers each |
1459 | hour, on the hour: |
2122 | hour, on the hour (with respect to UTC): |
1460 | |
2123 | |
1461 | ev_periodic_set (&periodic, 0., 3600., 0); |
2124 | ev_periodic_set (&periodic, 0., 3600., 0); |
1462 | |
2125 | |
1463 | This doesn't mean there will always be 3600 seconds in between triggers, |
2126 | This doesn't mean there will always be 3600 seconds in between triggers, |
1464 | but only that the callback will be called when the system time shows a |
2127 | but only that the callback will be called when the system time shows a |
1465 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2128 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1466 | by 3600. |
2129 | by 3600. |
1467 | |
2130 | |
1468 | Another way to think about it (for the mathematically inclined) is that |
2131 | Another way to think about it (for the mathematically inclined) is that |
1469 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2132 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1470 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2133 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1471 | |
2134 | |
1472 | For numerical stability it is preferable that the C<at> value is near |
2135 | For numerical stability it is preferable that the C<offset> value is near |
1473 | C<ev_now ()> (the current time), but there is no range requirement for |
2136 | C<ev_now ()> (the current time), but there is no range requirement for |
1474 | this value, and in fact is often specified as zero. |
2137 | this value, and in fact is often specified as zero. |
1475 | |
2138 | |
1476 | Note also that there is an upper limit to how often a timer can fire (CPU |
2139 | Note also that there is an upper limit to how often a timer can fire (CPU |
1477 | speed for example), so if C<interval> is very small then timing stability |
2140 | speed for example), so if C<interval> is very small then timing stability |
1478 | will of course deteriorate. Libev itself tries to be exact to be about one |
2141 | will of course deteriorate. Libev itself tries to be exact to be about one |
1479 | millisecond (if the OS supports it and the machine is fast enough). |
2142 | millisecond (if the OS supports it and the machine is fast enough). |
1480 | |
2143 | |
1481 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2144 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1482 | |
2145 | |
1483 | In this mode the values for C<interval> and C<at> are both being |
2146 | In this mode the values for C<interval> and C<offset> are both being |
1484 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2147 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1485 | reschedule callback will be called with the watcher as first, and the |
2148 | reschedule callback will be called with the watcher as first, and the |
1486 | current time as second argument. |
2149 | current time as second argument. |
1487 | |
2150 | |
1488 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2151 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1489 | ever, or make ANY event loop modifications whatsoever>. |
2152 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2153 | allowed by documentation here>. |
1490 | |
2154 | |
1491 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2155 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1492 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2156 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1493 | only event loop modification you are allowed to do). |
2157 | only event loop modification you are allowed to do). |
1494 | |
2158 | |
1495 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2159 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1496 | *w, ev_tstamp now)>, e.g.: |
2160 | *w, ev_tstamp now)>, e.g.: |
1497 | |
2161 | |
|
|
2162 | static ev_tstamp |
1498 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2163 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1499 | { |
2164 | { |
1500 | return now + 60.; |
2165 | return now + 60.; |
1501 | } |
2166 | } |
1502 | |
2167 | |
1503 | It must return the next time to trigger, based on the passed time value |
2168 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1523 | a different time than the last time it was called (e.g. in a crond like |
2188 | a different time than the last time it was called (e.g. in a crond like |
1524 | program when the crontabs have changed). |
2189 | program when the crontabs have changed). |
1525 | |
2190 | |
1526 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2191 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1527 | |
2192 | |
1528 | When active, returns the absolute time that the watcher is supposed to |
2193 | When active, returns the absolute time that the watcher is supposed |
1529 | trigger next. |
2194 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2195 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2196 | rescheduling modes. |
1530 | |
2197 | |
1531 | =item ev_tstamp offset [read-write] |
2198 | =item ev_tstamp offset [read-write] |
1532 | |
2199 | |
1533 | When repeating, this contains the offset value, otherwise this is the |
2200 | When repeating, this contains the offset value, otherwise this is the |
1534 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2201 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2202 | although libev might modify this value for better numerical stability). |
1535 | |
2203 | |
1536 | Can be modified any time, but changes only take effect when the periodic |
2204 | Can be modified any time, but changes only take effect when the periodic |
1537 | timer fires or C<ev_periodic_again> is being called. |
2205 | timer fires or C<ev_periodic_again> is being called. |
1538 | |
2206 | |
1539 | =item ev_tstamp interval [read-write] |
2207 | =item ev_tstamp interval [read-write] |
1540 | |
2208 | |
1541 | The current interval value. Can be modified any time, but changes only |
2209 | The current interval value. Can be modified any time, but changes only |
1542 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2210 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1543 | called. |
2211 | called. |
1544 | |
2212 | |
1545 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2213 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1546 | |
2214 | |
1547 | The current reschedule callback, or C<0>, if this functionality is |
2215 | The current reschedule callback, or C<0>, if this functionality is |
1548 | switched off. Can be changed any time, but changes only take effect when |
2216 | switched off. Can be changed any time, but changes only take effect when |
1549 | the periodic timer fires or C<ev_periodic_again> is being called. |
2217 | the periodic timer fires or C<ev_periodic_again> is being called. |
1550 | |
2218 | |
… | |
… | |
1555 | Example: Call a callback every hour, or, more precisely, whenever the |
2223 | Example: Call a callback every hour, or, more precisely, whenever the |
1556 | system time is divisible by 3600. The callback invocation times have |
2224 | system time is divisible by 3600. The callback invocation times have |
1557 | potentially a lot of jitter, but good long-term stability. |
2225 | potentially a lot of jitter, but good long-term stability. |
1558 | |
2226 | |
1559 | static void |
2227 | static void |
1560 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2228 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1561 | { |
2229 | { |
1562 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2230 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1563 | } |
2231 | } |
1564 | |
2232 | |
1565 | struct ev_periodic hourly_tick; |
2233 | ev_periodic hourly_tick; |
1566 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2234 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1567 | ev_periodic_start (loop, &hourly_tick); |
2235 | ev_periodic_start (loop, &hourly_tick); |
1568 | |
2236 | |
1569 | Example: The same as above, but use a reschedule callback to do it: |
2237 | Example: The same as above, but use a reschedule callback to do it: |
1570 | |
2238 | |
1571 | #include <math.h> |
2239 | #include <math.h> |
1572 | |
2240 | |
1573 | static ev_tstamp |
2241 | static ev_tstamp |
1574 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2242 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1575 | { |
2243 | { |
1576 | return now + (3600. - fmod (now, 3600.)); |
2244 | return now + (3600. - fmod (now, 3600.)); |
1577 | } |
2245 | } |
1578 | |
2246 | |
1579 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2247 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1580 | |
2248 | |
1581 | Example: Call a callback every hour, starting now: |
2249 | Example: Call a callback every hour, starting now: |
1582 | |
2250 | |
1583 | struct ev_periodic hourly_tick; |
2251 | ev_periodic hourly_tick; |
1584 | ev_periodic_init (&hourly_tick, clock_cb, |
2252 | ev_periodic_init (&hourly_tick, clock_cb, |
1585 | fmod (ev_now (loop), 3600.), 3600., 0); |
2253 | fmod (ev_now (loop), 3600.), 3600., 0); |
1586 | ev_periodic_start (loop, &hourly_tick); |
2254 | ev_periodic_start (loop, &hourly_tick); |
1587 | |
2255 | |
1588 | |
2256 | |
… | |
… | |
1591 | Signal watchers will trigger an event when the process receives a specific |
2259 | Signal watchers will trigger an event when the process receives a specific |
1592 | signal one or more times. Even though signals are very asynchronous, libev |
2260 | signal one or more times. Even though signals are very asynchronous, libev |
1593 | will try it's best to deliver signals synchronously, i.e. as part of the |
2261 | will try it's best to deliver signals synchronously, i.e. as part of the |
1594 | normal event processing, like any other event. |
2262 | normal event processing, like any other event. |
1595 | |
2263 | |
1596 | If you want signals asynchronously, just use C<sigaction> as you would |
2264 | If you want signals to be delivered truly asynchronously, just use |
1597 | do without libev and forget about sharing the signal. You can even use |
2265 | C<sigaction> as you would do without libev and forget about sharing |
1598 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2266 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2267 | synchronously wake up an event loop. |
1599 | |
2268 | |
1600 | You can configure as many watchers as you like per signal. Only when the |
2269 | You can configure as many watchers as you like for the same signal, but |
|
|
2270 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2271 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2272 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2273 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2274 | |
1601 | first watcher gets started will libev actually register a signal handler |
2275 | When the first watcher gets started will libev actually register something |
1602 | with the kernel (thus it coexists with your own signal handlers as long as |
2276 | with the kernel (thus it coexists with your own signal handlers as long as |
1603 | you don't register any with libev for the same signal). Similarly, when |
2277 | you don't register any with libev for the same signal). |
1604 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1605 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1606 | |
2278 | |
1607 | If possible and supported, libev will install its handlers with |
2279 | If possible and supported, libev will install its handlers with |
1608 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2280 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1609 | interrupted. If you have a problem with system calls getting interrupted by |
2281 | not be unduly interrupted. If you have a problem with system calls getting |
1610 | signals you can block all signals in an C<ev_check> watcher and unblock |
2282 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1611 | them in an C<ev_prepare> watcher. |
2283 | and unblock them in an C<ev_prepare> watcher. |
|
|
2284 | |
|
|
2285 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2286 | |
|
|
2287 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2288 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2289 | stopping it again), that is, libev might or might not block the signal, |
|
|
2290 | and might or might not set or restore the installed signal handler. |
|
|
2291 | |
|
|
2292 | While this does not matter for the signal disposition (libev never |
|
|
2293 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2294 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2295 | certain signals to be blocked. |
|
|
2296 | |
|
|
2297 | This means that before calling C<exec> (from the child) you should reset |
|
|
2298 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2299 | choice usually). |
|
|
2300 | |
|
|
2301 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2302 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2303 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2304 | |
|
|
2305 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2306 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2307 | the window of opportunity for problems, it will not go away, as libev |
|
|
2308 | I<has> to modify the signal mask, at least temporarily. |
|
|
2309 | |
|
|
2310 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2311 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2312 | is not a libev-specific thing, this is true for most event libraries. |
1612 | |
2313 | |
1613 | =head3 Watcher-Specific Functions and Data Members |
2314 | =head3 Watcher-Specific Functions and Data Members |
1614 | |
2315 | |
1615 | =over 4 |
2316 | =over 4 |
1616 | |
2317 | |
… | |
… | |
1630 | =head3 Examples |
2331 | =head3 Examples |
1631 | |
2332 | |
1632 | Example: Try to exit cleanly on SIGINT. |
2333 | Example: Try to exit cleanly on SIGINT. |
1633 | |
2334 | |
1634 | static void |
2335 | static void |
1635 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2336 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1636 | { |
2337 | { |
1637 | ev_unloop (loop, EVUNLOOP_ALL); |
2338 | ev_break (loop, EVBREAK_ALL); |
1638 | } |
2339 | } |
1639 | |
2340 | |
1640 | struct ev_signal signal_watcher; |
2341 | ev_signal signal_watcher; |
1641 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2342 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1642 | ev_signal_start (loop, &signal_watcher); |
2343 | ev_signal_start (loop, &signal_watcher); |
1643 | |
2344 | |
1644 | |
2345 | |
1645 | =head2 C<ev_child> - watch out for process status changes |
2346 | =head2 C<ev_child> - watch out for process status changes |
… | |
… | |
1648 | some child status changes (most typically when a child of yours dies or |
2349 | some child status changes (most typically when a child of yours dies or |
1649 | exits). It is permissible to install a child watcher I<after> the child |
2350 | exits). It is permissible to install a child watcher I<after> the child |
1650 | has been forked (which implies it might have already exited), as long |
2351 | has been forked (which implies it might have already exited), as long |
1651 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2352 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1652 | forking and then immediately registering a watcher for the child is fine, |
2353 | forking and then immediately registering a watcher for the child is fine, |
1653 | but forking and registering a watcher a few event loop iterations later is |
2354 | but forking and registering a watcher a few event loop iterations later or |
1654 | not. |
2355 | in the next callback invocation is not. |
1655 | |
2356 | |
1656 | Only the default event loop is capable of handling signals, and therefore |
2357 | Only the default event loop is capable of handling signals, and therefore |
1657 | you can only register child watchers in the default event loop. |
2358 | you can only register child watchers in the default event loop. |
1658 | |
2359 | |
|
|
2360 | Due to some design glitches inside libev, child watchers will always be |
|
|
2361 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2362 | libev) |
|
|
2363 | |
1659 | =head3 Process Interaction |
2364 | =head3 Process Interaction |
1660 | |
2365 | |
1661 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2366 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1662 | initialised. This is necessary to guarantee proper behaviour even if |
2367 | initialised. This is necessary to guarantee proper behaviour even if the |
1663 | the first child watcher is started after the child exits. The occurrence |
2368 | first child watcher is started after the child exits. The occurrence |
1664 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2369 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1665 | synchronously as part of the event loop processing. Libev always reaps all |
2370 | synchronously as part of the event loop processing. Libev always reaps all |
1666 | children, even ones not watched. |
2371 | children, even ones not watched. |
1667 | |
2372 | |
1668 | =head3 Overriding the Built-In Processing |
2373 | =head3 Overriding the Built-In Processing |
… | |
… | |
1678 | =head3 Stopping the Child Watcher |
2383 | =head3 Stopping the Child Watcher |
1679 | |
2384 | |
1680 | Currently, the child watcher never gets stopped, even when the |
2385 | Currently, the child watcher never gets stopped, even when the |
1681 | child terminates, so normally one needs to stop the watcher in the |
2386 | child terminates, so normally one needs to stop the watcher in the |
1682 | callback. Future versions of libev might stop the watcher automatically |
2387 | callback. Future versions of libev might stop the watcher automatically |
1683 | when a child exit is detected. |
2388 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2389 | problem). |
1684 | |
2390 | |
1685 | =head3 Watcher-Specific Functions and Data Members |
2391 | =head3 Watcher-Specific Functions and Data Members |
1686 | |
2392 | |
1687 | =over 4 |
2393 | =over 4 |
1688 | |
2394 | |
… | |
… | |
1720 | its completion. |
2426 | its completion. |
1721 | |
2427 | |
1722 | ev_child cw; |
2428 | ev_child cw; |
1723 | |
2429 | |
1724 | static void |
2430 | static void |
1725 | child_cb (EV_P_ struct ev_child *w, int revents) |
2431 | child_cb (EV_P_ ev_child *w, int revents) |
1726 | { |
2432 | { |
1727 | ev_child_stop (EV_A_ w); |
2433 | ev_child_stop (EV_A_ w); |
1728 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2434 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1729 | } |
2435 | } |
1730 | |
2436 | |
… | |
… | |
1745 | |
2451 | |
1746 | |
2452 | |
1747 | =head2 C<ev_stat> - did the file attributes just change? |
2453 | =head2 C<ev_stat> - did the file attributes just change? |
1748 | |
2454 | |
1749 | This watches a file system path for attribute changes. That is, it calls |
2455 | This watches a file system path for attribute changes. That is, it calls |
1750 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2456 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1751 | compared to the last time, invoking the callback if it did. |
2457 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2458 | it did. |
1752 | |
2459 | |
1753 | The path does not need to exist: changing from "path exists" to "path does |
2460 | The path does not need to exist: changing from "path exists" to "path does |
1754 | not exist" is a status change like any other. The condition "path does |
2461 | not exist" is a status change like any other. The condition "path does not |
1755 | not exist" is signified by the C<st_nlink> field being zero (which is |
2462 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1756 | otherwise always forced to be at least one) and all the other fields of |
2463 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1757 | the stat buffer having unspecified contents. |
2464 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2465 | contents. |
1758 | |
2466 | |
1759 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2467 | The path I<must not> end in a slash or contain special components such as |
|
|
2468 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1760 | relative and your working directory changes, the behaviour is undefined. |
2469 | your working directory changes, then the behaviour is undefined. |
1761 | |
2470 | |
1762 | Since there is no standard kernel interface to do this, the portable |
2471 | Since there is no portable change notification interface available, the |
1763 | implementation simply calls C<stat (2)> regularly on the path to see if |
2472 | portable implementation simply calls C<stat(2)> regularly on the path |
1764 | it changed somehow. You can specify a recommended polling interval for |
2473 | to see if it changed somehow. You can specify a recommended polling |
1765 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2474 | interval for this case. If you specify a polling interval of C<0> (highly |
1766 | then a I<suitable, unspecified default> value will be used (which |
2475 | recommended!) then a I<suitable, unspecified default> value will be used |
1767 | you can expect to be around five seconds, although this might change |
2476 | (which you can expect to be around five seconds, although this might |
1768 | dynamically). Libev will also impose a minimum interval which is currently |
2477 | change dynamically). Libev will also impose a minimum interval which is |
1769 | around C<0.1>, but thats usually overkill. |
2478 | currently around C<0.1>, but that's usually overkill. |
1770 | |
2479 | |
1771 | This watcher type is not meant for massive numbers of stat watchers, |
2480 | This watcher type is not meant for massive numbers of stat watchers, |
1772 | as even with OS-supported change notifications, this can be |
2481 | as even with OS-supported change notifications, this can be |
1773 | resource-intensive. |
2482 | resource-intensive. |
1774 | |
2483 | |
1775 | At the time of this writing, the only OS-specific interface implemented |
2484 | At the time of this writing, the only OS-specific interface implemented |
1776 | is the Linux inotify interface (implementing kqueue support is left as |
2485 | is the Linux inotify interface (implementing kqueue support is left as an |
1777 | an exercise for the reader. Note, however, that the author sees no way |
2486 | exercise for the reader. Note, however, that the author sees no way of |
1778 | of implementing C<ev_stat> semantics with kqueue). |
2487 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1779 | |
2488 | |
1780 | =head3 ABI Issues (Largefile Support) |
2489 | =head3 ABI Issues (Largefile Support) |
1781 | |
2490 | |
1782 | Libev by default (unless the user overrides this) uses the default |
2491 | Libev by default (unless the user overrides this) uses the default |
1783 | compilation environment, which means that on systems with large file |
2492 | compilation environment, which means that on systems with large file |
1784 | support disabled by default, you get the 32 bit version of the stat |
2493 | support disabled by default, you get the 32 bit version of the stat |
1785 | structure. When using the library from programs that change the ABI to |
2494 | structure. When using the library from programs that change the ABI to |
1786 | use 64 bit file offsets the programs will fail. In that case you have to |
2495 | use 64 bit file offsets the programs will fail. In that case you have to |
1787 | compile libev with the same flags to get binary compatibility. This is |
2496 | compile libev with the same flags to get binary compatibility. This is |
1788 | obviously the case with any flags that change the ABI, but the problem is |
2497 | obviously the case with any flags that change the ABI, but the problem is |
1789 | most noticeably disabled with ev_stat and large file support. |
2498 | most noticeably displayed with ev_stat and large file support. |
1790 | |
2499 | |
1791 | The solution for this is to lobby your distribution maker to make large |
2500 | The solution for this is to lobby your distribution maker to make large |
1792 | file interfaces available by default (as e.g. FreeBSD does) and not |
2501 | file interfaces available by default (as e.g. FreeBSD does) and not |
1793 | optional. Libev cannot simply switch on large file support because it has |
2502 | optional. Libev cannot simply switch on large file support because it has |
1794 | to exchange stat structures with application programs compiled using the |
2503 | to exchange stat structures with application programs compiled using the |
1795 | default compilation environment. |
2504 | default compilation environment. |
1796 | |
2505 | |
1797 | =head3 Inotify and Kqueue |
2506 | =head3 Inotify and Kqueue |
1798 | |
2507 | |
1799 | When C<inotify (7)> support has been compiled into libev (generally only |
2508 | When C<inotify (7)> support has been compiled into libev and present at |
1800 | available with Linux) and present at runtime, it will be used to speed up |
2509 | runtime, it will be used to speed up change detection where possible. The |
1801 | change detection where possible. The inotify descriptor will be created lazily |
2510 | inotify descriptor will be created lazily when the first C<ev_stat> |
1802 | when the first C<ev_stat> watcher is being started. |
2511 | watcher is being started. |
1803 | |
2512 | |
1804 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2513 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1805 | except that changes might be detected earlier, and in some cases, to avoid |
2514 | except that changes might be detected earlier, and in some cases, to avoid |
1806 | making regular C<stat> calls. Even in the presence of inotify support |
2515 | making regular C<stat> calls. Even in the presence of inotify support |
1807 | there are many cases where libev has to resort to regular C<stat> polling, |
2516 | there are many cases where libev has to resort to regular C<stat> polling, |
1808 | but as long as the path exists, libev usually gets away without polling. |
2517 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2518 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2519 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2520 | xfs are fully working) libev usually gets away without polling. |
1809 | |
2521 | |
1810 | There is no support for kqueue, as apparently it cannot be used to |
2522 | There is no support for kqueue, as apparently it cannot be used to |
1811 | implement this functionality, due to the requirement of having a file |
2523 | implement this functionality, due to the requirement of having a file |
1812 | descriptor open on the object at all times, and detecting renames, unlinks |
2524 | descriptor open on the object at all times, and detecting renames, unlinks |
1813 | etc. is difficult. |
2525 | etc. is difficult. |
1814 | |
2526 | |
|
|
2527 | =head3 C<stat ()> is a synchronous operation |
|
|
2528 | |
|
|
2529 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2530 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2531 | ()>, which is a synchronous operation. |
|
|
2532 | |
|
|
2533 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2534 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2535 | as the path data is usually in memory already (except when starting the |
|
|
2536 | watcher). |
|
|
2537 | |
|
|
2538 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2539 | time due to network issues, and even under good conditions, a stat call |
|
|
2540 | often takes multiple milliseconds. |
|
|
2541 | |
|
|
2542 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2543 | paths, although this is fully supported by libev. |
|
|
2544 | |
1815 | =head3 The special problem of stat time resolution |
2545 | =head3 The special problem of stat time resolution |
1816 | |
2546 | |
1817 | The C<stat ()> system call only supports full-second resolution portably, and |
2547 | The C<stat ()> system call only supports full-second resolution portably, |
1818 | even on systems where the resolution is higher, most file systems still |
2548 | and even on systems where the resolution is higher, most file systems |
1819 | only support whole seconds. |
2549 | still only support whole seconds. |
1820 | |
2550 | |
1821 | That means that, if the time is the only thing that changes, you can |
2551 | That means that, if the time is the only thing that changes, you can |
1822 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2552 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1823 | calls your callback, which does something. When there is another update |
2553 | calls your callback, which does something. When there is another update |
1824 | within the same second, C<ev_stat> will be unable to detect unless the |
2554 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1967 | |
2697 | |
1968 | =head3 Watcher-Specific Functions and Data Members |
2698 | =head3 Watcher-Specific Functions and Data Members |
1969 | |
2699 | |
1970 | =over 4 |
2700 | =over 4 |
1971 | |
2701 | |
1972 | =item ev_idle_init (ev_signal *, callback) |
2702 | =item ev_idle_init (ev_idle *, callback) |
1973 | |
2703 | |
1974 | Initialises and configures the idle watcher - it has no parameters of any |
2704 | Initialises and configures the idle watcher - it has no parameters of any |
1975 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2705 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1976 | believe me. |
2706 | believe me. |
1977 | |
2707 | |
… | |
… | |
1981 | |
2711 | |
1982 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2712 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1983 | callback, free it. Also, use no error checking, as usual. |
2713 | callback, free it. Also, use no error checking, as usual. |
1984 | |
2714 | |
1985 | static void |
2715 | static void |
1986 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2716 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1987 | { |
2717 | { |
1988 | free (w); |
2718 | free (w); |
1989 | // now do something you wanted to do when the program has |
2719 | // now do something you wanted to do when the program has |
1990 | // no longer anything immediate to do. |
2720 | // no longer anything immediate to do. |
1991 | } |
2721 | } |
1992 | |
2722 | |
1993 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2723 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1994 | ev_idle_init (idle_watcher, idle_cb); |
2724 | ev_idle_init (idle_watcher, idle_cb); |
1995 | ev_idle_start (loop, idle_cb); |
2725 | ev_idle_start (loop, idle_watcher); |
1996 | |
2726 | |
1997 | |
2727 | |
1998 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2728 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1999 | |
2729 | |
2000 | Prepare and check watchers are usually (but not always) used in pairs: |
2730 | Prepare and check watchers are usually (but not always) used in pairs: |
2001 | prepare watchers get invoked before the process blocks and check watchers |
2731 | prepare watchers get invoked before the process blocks and check watchers |
2002 | afterwards. |
2732 | afterwards. |
2003 | |
2733 | |
2004 | You I<must not> call C<ev_loop> or similar functions that enter |
2734 | You I<must not> call C<ev_run> or similar functions that enter |
2005 | the current event loop from either C<ev_prepare> or C<ev_check> |
2735 | the current event loop from either C<ev_prepare> or C<ev_check> |
2006 | watchers. Other loops than the current one are fine, however. The |
2736 | watchers. Other loops than the current one are fine, however. The |
2007 | rationale behind this is that you do not need to check for recursion in |
2737 | rationale behind this is that you do not need to check for recursion in |
2008 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2738 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2009 | C<ev_check> so if you have one watcher of each kind they will always be |
2739 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2079 | |
2809 | |
2080 | static ev_io iow [nfd]; |
2810 | static ev_io iow [nfd]; |
2081 | static ev_timer tw; |
2811 | static ev_timer tw; |
2082 | |
2812 | |
2083 | static void |
2813 | static void |
2084 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2814 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2085 | { |
2815 | { |
2086 | } |
2816 | } |
2087 | |
2817 | |
2088 | // create io watchers for each fd and a timer before blocking |
2818 | // create io watchers for each fd and a timer before blocking |
2089 | static void |
2819 | static void |
2090 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2820 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2091 | { |
2821 | { |
2092 | int timeout = 3600000; |
2822 | int timeout = 3600000; |
2093 | struct pollfd fds [nfd]; |
2823 | struct pollfd fds [nfd]; |
2094 | // actual code will need to loop here and realloc etc. |
2824 | // actual code will need to loop here and realloc etc. |
2095 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2825 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2096 | |
2826 | |
2097 | /* the callback is illegal, but won't be called as we stop during check */ |
2827 | /* the callback is illegal, but won't be called as we stop during check */ |
2098 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2828 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2099 | ev_timer_start (loop, &tw); |
2829 | ev_timer_start (loop, &tw); |
2100 | |
2830 | |
2101 | // create one ev_io per pollfd |
2831 | // create one ev_io per pollfd |
2102 | for (int i = 0; i < nfd; ++i) |
2832 | for (int i = 0; i < nfd; ++i) |
2103 | { |
2833 | { |
… | |
… | |
2110 | } |
2840 | } |
2111 | } |
2841 | } |
2112 | |
2842 | |
2113 | // stop all watchers after blocking |
2843 | // stop all watchers after blocking |
2114 | static void |
2844 | static void |
2115 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2845 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2116 | { |
2846 | { |
2117 | ev_timer_stop (loop, &tw); |
2847 | ev_timer_stop (loop, &tw); |
2118 | |
2848 | |
2119 | for (int i = 0; i < nfd; ++i) |
2849 | for (int i = 0; i < nfd; ++i) |
2120 | { |
2850 | { |
… | |
… | |
2177 | |
2907 | |
2178 | if (timeout >= 0) |
2908 | if (timeout >= 0) |
2179 | // create/start timer |
2909 | // create/start timer |
2180 | |
2910 | |
2181 | // poll |
2911 | // poll |
2182 | ev_loop (EV_A_ 0); |
2912 | ev_run (EV_A_ 0); |
2183 | |
2913 | |
2184 | // stop timer again |
2914 | // stop timer again |
2185 | if (timeout >= 0) |
2915 | if (timeout >= 0) |
2186 | ev_timer_stop (EV_A_ &to); |
2916 | ev_timer_stop (EV_A_ &to); |
2187 | |
2917 | |
… | |
… | |
2216 | some fds have to be watched and handled very quickly (with low latency), |
2946 | some fds have to be watched and handled very quickly (with low latency), |
2217 | and even priorities and idle watchers might have too much overhead. In |
2947 | and even priorities and idle watchers might have too much overhead. In |
2218 | this case you would put all the high priority stuff in one loop and all |
2948 | this case you would put all the high priority stuff in one loop and all |
2219 | the rest in a second one, and embed the second one in the first. |
2949 | the rest in a second one, and embed the second one in the first. |
2220 | |
2950 | |
2221 | As long as the watcher is active, the callback will be invoked every time |
2951 | As long as the watcher is active, the callback will be invoked every |
2222 | there might be events pending in the embedded loop. The callback must then |
2952 | time there might be events pending in the embedded loop. The callback |
2223 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2953 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2224 | their callbacks (you could also start an idle watcher to give the embedded |
2954 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2225 | loop strictly lower priority for example). You can also set the callback |
2955 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2226 | to C<0>, in which case the embed watcher will automatically execute the |
2956 | to give the embedded loop strictly lower priority for example). |
2227 | embedded loop sweep. |
|
|
2228 | |
2957 | |
2229 | As long as the watcher is started it will automatically handle events. The |
2958 | You can also set the callback to C<0>, in which case the embed watcher |
2230 | callback will be invoked whenever some events have been handled. You can |
2959 | will automatically execute the embedded loop sweep whenever necessary. |
2231 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2232 | interested in that. |
|
|
2233 | |
2960 | |
2234 | Also, there have not currently been made special provisions for forking: |
2961 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2235 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2962 | is active, i.e., the embedded loop will automatically be forked when the |
2236 | but you will also have to stop and restart any C<ev_embed> watchers |
2963 | embedding loop forks. In other cases, the user is responsible for calling |
2237 | yourself - but you can use a fork watcher to handle this automatically, |
2964 | C<ev_loop_fork> on the embedded loop. |
2238 | and future versions of libev might do just that. |
|
|
2239 | |
2965 | |
2240 | Unfortunately, not all backends are embeddable: only the ones returned by |
2966 | Unfortunately, not all backends are embeddable: only the ones returned by |
2241 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2967 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2242 | portable one. |
2968 | portable one. |
2243 | |
2969 | |
… | |
… | |
2269 | if you do not want that, you need to temporarily stop the embed watcher). |
2995 | if you do not want that, you need to temporarily stop the embed watcher). |
2270 | |
2996 | |
2271 | =item ev_embed_sweep (loop, ev_embed *) |
2997 | =item ev_embed_sweep (loop, ev_embed *) |
2272 | |
2998 | |
2273 | Make a single, non-blocking sweep over the embedded loop. This works |
2999 | Make a single, non-blocking sweep over the embedded loop. This works |
2274 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3000 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2275 | appropriate way for embedded loops. |
3001 | appropriate way for embedded loops. |
2276 | |
3002 | |
2277 | =item struct ev_loop *other [read-only] |
3003 | =item struct ev_loop *other [read-only] |
2278 | |
3004 | |
2279 | The embedded event loop. |
3005 | The embedded event loop. |
… | |
… | |
2288 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
3014 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2289 | used). |
3015 | used). |
2290 | |
3016 | |
2291 | struct ev_loop *loop_hi = ev_default_init (0); |
3017 | struct ev_loop *loop_hi = ev_default_init (0); |
2292 | struct ev_loop *loop_lo = 0; |
3018 | struct ev_loop *loop_lo = 0; |
2293 | struct ev_embed embed; |
3019 | ev_embed embed; |
2294 | |
3020 | |
2295 | // see if there is a chance of getting one that works |
3021 | // see if there is a chance of getting one that works |
2296 | // (remember that a flags value of 0 means autodetection) |
3022 | // (remember that a flags value of 0 means autodetection) |
2297 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3023 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2298 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3024 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2312 | kqueue implementation). Store the kqueue/socket-only event loop in |
3038 | kqueue implementation). Store the kqueue/socket-only event loop in |
2313 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3039 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2314 | |
3040 | |
2315 | struct ev_loop *loop = ev_default_init (0); |
3041 | struct ev_loop *loop = ev_default_init (0); |
2316 | struct ev_loop *loop_socket = 0; |
3042 | struct ev_loop *loop_socket = 0; |
2317 | struct ev_embed embed; |
3043 | ev_embed embed; |
2318 | |
3044 | |
2319 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3045 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2320 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3046 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2321 | { |
3047 | { |
2322 | ev_embed_init (&embed, 0, loop_socket); |
3048 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2337 | event loop blocks next and before C<ev_check> watchers are being called, |
3063 | event loop blocks next and before C<ev_check> watchers are being called, |
2338 | and only in the child after the fork. If whoever good citizen calling |
3064 | and only in the child after the fork. If whoever good citizen calling |
2339 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3065 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2340 | handlers will be invoked, too, of course. |
3066 | handlers will be invoked, too, of course. |
2341 | |
3067 | |
|
|
3068 | =head3 The special problem of life after fork - how is it possible? |
|
|
3069 | |
|
|
3070 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3071 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3072 | sequence should be handled by libev without any problems. |
|
|
3073 | |
|
|
3074 | This changes when the application actually wants to do event handling |
|
|
3075 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3076 | fork. |
|
|
3077 | |
|
|
3078 | The default mode of operation (for libev, with application help to detect |
|
|
3079 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3080 | when I<either> the parent I<or> the child process continues. |
|
|
3081 | |
|
|
3082 | When both processes want to continue using libev, then this is usually the |
|
|
3083 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3084 | supposed to continue with all watchers in place as before, while the other |
|
|
3085 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3086 | |
|
|
3087 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3088 | simply create a new event loop, which of course will be "empty", and |
|
|
3089 | use that for new watchers. This has the advantage of not touching more |
|
|
3090 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3091 | disadvantage of having to use multiple event loops (which do not support |
|
|
3092 | signal watchers). |
|
|
3093 | |
|
|
3094 | When this is not possible, or you want to use the default loop for |
|
|
3095 | other reasons, then in the process that wants to start "fresh", call |
|
|
3096 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3097 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3098 | watchers, so you have to be careful not to execute code that modifies |
|
|
3099 | those watchers. Note also that in that case, you have to re-register any |
|
|
3100 | signal watchers. |
|
|
3101 | |
2342 | =head3 Watcher-Specific Functions and Data Members |
3102 | =head3 Watcher-Specific Functions and Data Members |
2343 | |
3103 | |
2344 | =over 4 |
3104 | =over 4 |
2345 | |
3105 | |
2346 | =item ev_fork_init (ev_signal *, callback) |
3106 | =item ev_fork_init (ev_fork *, callback) |
2347 | |
3107 | |
2348 | Initialises and configures the fork watcher - it has no parameters of any |
3108 | Initialises and configures the fork watcher - it has no parameters of any |
2349 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3109 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2350 | believe me. |
3110 | really. |
2351 | |
3111 | |
2352 | =back |
3112 | =back |
2353 | |
3113 | |
2354 | |
3114 | |
|
|
3115 | =head2 C<ev_cleanup> - even the best things end |
|
|
3116 | |
|
|
3117 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3118 | by a call to C<ev_loop_destroy>. |
|
|
3119 | |
|
|
3120 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3121 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3122 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3123 | loop when you want them to be invoked. |
|
|
3124 | |
|
|
3125 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3126 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3127 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3128 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3129 | |
|
|
3130 | =head3 Watcher-Specific Functions and Data Members |
|
|
3131 | |
|
|
3132 | =over 4 |
|
|
3133 | |
|
|
3134 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3135 | |
|
|
3136 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3137 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3138 | pointless, I assure you. |
|
|
3139 | |
|
|
3140 | =back |
|
|
3141 | |
|
|
3142 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3143 | cleanup functions are called. |
|
|
3144 | |
|
|
3145 | static void |
|
|
3146 | program_exits (void) |
|
|
3147 | { |
|
|
3148 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3149 | } |
|
|
3150 | |
|
|
3151 | ... |
|
|
3152 | atexit (program_exits); |
|
|
3153 | |
|
|
3154 | |
2355 | =head2 C<ev_async> - how to wake up another event loop |
3155 | =head2 C<ev_async> - how to wake up an event loop |
2356 | |
3156 | |
2357 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3157 | In general, you cannot use an C<ev_run> from multiple threads or other |
2358 | asynchronous sources such as signal handlers (as opposed to multiple event |
3158 | asynchronous sources such as signal handlers (as opposed to multiple event |
2359 | loops - those are of course safe to use in different threads). |
3159 | loops - those are of course safe to use in different threads). |
2360 | |
3160 | |
2361 | Sometimes, however, you need to wake up another event loop you do not |
3161 | Sometimes, however, you need to wake up an event loop you do not control, |
2362 | control, for example because it belongs to another thread. This is what |
3162 | for example because it belongs to another thread. This is what C<ev_async> |
2363 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3163 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2364 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3164 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2365 | safe. |
|
|
2366 | |
3165 | |
2367 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3166 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2368 | too, are asynchronous in nature, and signals, too, will be compressed |
3167 | too, are asynchronous in nature, and signals, too, will be compressed |
2369 | (i.e. the number of callback invocations may be less than the number of |
3168 | (i.e. the number of callback invocations may be less than the number of |
2370 | C<ev_async_sent> calls). |
3169 | C<ev_async_sent> calls). |
… | |
… | |
2375 | =head3 Queueing |
3174 | =head3 Queueing |
2376 | |
3175 | |
2377 | C<ev_async> does not support queueing of data in any way. The reason |
3176 | C<ev_async> does not support queueing of data in any way. The reason |
2378 | is that the author does not know of a simple (or any) algorithm for a |
3177 | is that the author does not know of a simple (or any) algorithm for a |
2379 | multiple-writer-single-reader queue that works in all cases and doesn't |
3178 | multiple-writer-single-reader queue that works in all cases and doesn't |
2380 | need elaborate support such as pthreads. |
3179 | need elaborate support such as pthreads or unportable memory access |
|
|
3180 | semantics. |
2381 | |
3181 | |
2382 | That means that if you want to queue data, you have to provide your own |
3182 | That means that if you want to queue data, you have to provide your own |
2383 | queue. But at least I can tell you how to implement locking around your |
3183 | queue. But at least I can tell you how to implement locking around your |
2384 | queue: |
3184 | queue: |
2385 | |
3185 | |
… | |
… | |
2463 | =over 4 |
3263 | =over 4 |
2464 | |
3264 | |
2465 | =item ev_async_init (ev_async *, callback) |
3265 | =item ev_async_init (ev_async *, callback) |
2466 | |
3266 | |
2467 | Initialises and configures the async watcher - it has no parameters of any |
3267 | Initialises and configures the async watcher - it has no parameters of any |
2468 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3268 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2469 | trust me. |
3269 | trust me. |
2470 | |
3270 | |
2471 | =item ev_async_send (loop, ev_async *) |
3271 | =item ev_async_send (loop, ev_async *) |
2472 | |
3272 | |
2473 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3273 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2474 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3274 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2475 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3275 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2476 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3276 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2477 | section below on what exactly this means). |
3277 | section below on what exactly this means). |
2478 | |
3278 | |
|
|
3279 | Note that, as with other watchers in libev, multiple events might get |
|
|
3280 | compressed into a single callback invocation (another way to look at this |
|
|
3281 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3282 | reset when the event loop detects that). |
|
|
3283 | |
2479 | This call incurs the overhead of a system call only once per loop iteration, |
3284 | This call incurs the overhead of a system call only once per event loop |
2480 | so while the overhead might be noticeable, it doesn't apply to repeated |
3285 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2481 | calls to C<ev_async_send>. |
3286 | repeated calls to C<ev_async_send> for the same event loop. |
2482 | |
3287 | |
2483 | =item bool = ev_async_pending (ev_async *) |
3288 | =item bool = ev_async_pending (ev_async *) |
2484 | |
3289 | |
2485 | Returns a non-zero value when C<ev_async_send> has been called on the |
3290 | Returns a non-zero value when C<ev_async_send> has been called on the |
2486 | watcher but the event has not yet been processed (or even noted) by the |
3291 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2489 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3294 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2490 | the loop iterates next and checks for the watcher to have become active, |
3295 | the loop iterates next and checks for the watcher to have become active, |
2491 | it will reset the flag again. C<ev_async_pending> can be used to very |
3296 | it will reset the flag again. C<ev_async_pending> can be used to very |
2492 | quickly check whether invoking the loop might be a good idea. |
3297 | quickly check whether invoking the loop might be a good idea. |
2493 | |
3298 | |
2494 | Not that this does I<not> check whether the watcher itself is pending, only |
3299 | Not that this does I<not> check whether the watcher itself is pending, |
2495 | whether it has been requested to make this watcher pending. |
3300 | only whether it has been requested to make this watcher pending: there |
|
|
3301 | is a time window between the event loop checking and resetting the async |
|
|
3302 | notification, and the callback being invoked. |
2496 | |
3303 | |
2497 | =back |
3304 | =back |
2498 | |
3305 | |
2499 | |
3306 | |
2500 | =head1 OTHER FUNCTIONS |
3307 | =head1 OTHER FUNCTIONS |
… | |
… | |
2517 | |
3324 | |
2518 | If C<timeout> is less than 0, then no timeout watcher will be |
3325 | If C<timeout> is less than 0, then no timeout watcher will be |
2519 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3326 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2520 | repeat = 0) will be started. C<0> is a valid timeout. |
3327 | repeat = 0) will be started. C<0> is a valid timeout. |
2521 | |
3328 | |
2522 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3329 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2523 | passed an C<revents> set like normal event callbacks (a combination of |
3330 | passed an C<revents> set like normal event callbacks (a combination of |
2524 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3331 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2525 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3332 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2526 | a timeout and an io event at the same time - you probably should give io |
3333 | a timeout and an io event at the same time - you probably should give io |
2527 | events precedence. |
3334 | events precedence. |
2528 | |
3335 | |
2529 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3336 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2530 | |
3337 | |
2531 | static void stdin_ready (int revents, void *arg) |
3338 | static void stdin_ready (int revents, void *arg) |
2532 | { |
3339 | { |
2533 | if (revents & EV_READ) |
3340 | if (revents & EV_READ) |
2534 | /* stdin might have data for us, joy! */; |
3341 | /* stdin might have data for us, joy! */; |
2535 | else if (revents & EV_TIMEOUT) |
3342 | else if (revents & EV_TIMER) |
2536 | /* doh, nothing entered */; |
3343 | /* doh, nothing entered */; |
2537 | } |
3344 | } |
2538 | |
3345 | |
2539 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3346 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2540 | |
3347 | |
2541 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2542 | |
|
|
2543 | Feeds the given event set into the event loop, as if the specified event |
|
|
2544 | had happened for the specified watcher (which must be a pointer to an |
|
|
2545 | initialised but not necessarily started event watcher). |
|
|
2546 | |
|
|
2547 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3348 | =item ev_feed_fd_event (loop, int fd, int revents) |
2548 | |
3349 | |
2549 | Feed an event on the given fd, as if a file descriptor backend detected |
3350 | Feed an event on the given fd, as if a file descriptor backend detected |
2550 | the given events it. |
3351 | the given events it. |
2551 | |
3352 | |
2552 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3353 | =item ev_feed_signal_event (loop, int signum) |
2553 | |
3354 | |
2554 | Feed an event as if the given signal occurred (C<loop> must be the default |
3355 | Feed an event as if the given signal occurred (C<loop> must be the default |
2555 | loop!). |
3356 | loop!). |
2556 | |
3357 | |
2557 | =back |
3358 | =back |
… | |
… | |
2637 | |
3438 | |
2638 | =over 4 |
3439 | =over 4 |
2639 | |
3440 | |
2640 | =item ev::TYPE::TYPE () |
3441 | =item ev::TYPE::TYPE () |
2641 | |
3442 | |
2642 | =item ev::TYPE::TYPE (struct ev_loop *) |
3443 | =item ev::TYPE::TYPE (loop) |
2643 | |
3444 | |
2644 | =item ev::TYPE::~TYPE |
3445 | =item ev::TYPE::~TYPE |
2645 | |
3446 | |
2646 | The constructor (optionally) takes an event loop to associate the watcher |
3447 | The constructor (optionally) takes an event loop to associate the watcher |
2647 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3448 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2679 | |
3480 | |
2680 | myclass obj; |
3481 | myclass obj; |
2681 | ev::io iow; |
3482 | ev::io iow; |
2682 | iow.set <myclass, &myclass::io_cb> (&obj); |
3483 | iow.set <myclass, &myclass::io_cb> (&obj); |
2683 | |
3484 | |
|
|
3485 | =item w->set (object *) |
|
|
3486 | |
|
|
3487 | This is a variation of a method callback - leaving out the method to call |
|
|
3488 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3489 | functor objects without having to manually specify the C<operator ()> all |
|
|
3490 | the time. Incidentally, you can then also leave out the template argument |
|
|
3491 | list. |
|
|
3492 | |
|
|
3493 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3494 | int revents)>. |
|
|
3495 | |
|
|
3496 | See the method-C<set> above for more details. |
|
|
3497 | |
|
|
3498 | Example: use a functor object as callback. |
|
|
3499 | |
|
|
3500 | struct myfunctor |
|
|
3501 | { |
|
|
3502 | void operator() (ev::io &w, int revents) |
|
|
3503 | { |
|
|
3504 | ... |
|
|
3505 | } |
|
|
3506 | } |
|
|
3507 | |
|
|
3508 | myfunctor f; |
|
|
3509 | |
|
|
3510 | ev::io w; |
|
|
3511 | w.set (&f); |
|
|
3512 | |
2684 | =item w->set<function> (void *data = 0) |
3513 | =item w->set<function> (void *data = 0) |
2685 | |
3514 | |
2686 | Also sets a callback, but uses a static method or plain function as |
3515 | Also sets a callback, but uses a static method or plain function as |
2687 | callback. The optional C<data> argument will be stored in the watcher's |
3516 | callback. The optional C<data> argument will be stored in the watcher's |
2688 | C<data> member and is free for you to use. |
3517 | C<data> member and is free for you to use. |
… | |
… | |
2694 | Example: Use a plain function as callback. |
3523 | Example: Use a plain function as callback. |
2695 | |
3524 | |
2696 | static void io_cb (ev::io &w, int revents) { } |
3525 | static void io_cb (ev::io &w, int revents) { } |
2697 | iow.set <io_cb> (); |
3526 | iow.set <io_cb> (); |
2698 | |
3527 | |
2699 | =item w->set (struct ev_loop *) |
3528 | =item w->set (loop) |
2700 | |
3529 | |
2701 | Associates a different C<struct ev_loop> with this watcher. You can only |
3530 | Associates a different C<struct ev_loop> with this watcher. You can only |
2702 | do this when the watcher is inactive (and not pending either). |
3531 | do this when the watcher is inactive (and not pending either). |
2703 | |
3532 | |
2704 | =item w->set ([arguments]) |
3533 | =item w->set ([arguments]) |
2705 | |
3534 | |
2706 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3535 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2707 | called at least once. Unlike the C counterpart, an active watcher gets |
3536 | method or a suitable start method must be called at least once. Unlike the |
2708 | automatically stopped and restarted when reconfiguring it with this |
3537 | C counterpart, an active watcher gets automatically stopped and restarted |
2709 | method. |
3538 | when reconfiguring it with this method. |
2710 | |
3539 | |
2711 | =item w->start () |
3540 | =item w->start () |
2712 | |
3541 | |
2713 | Starts the watcher. Note that there is no C<loop> argument, as the |
3542 | Starts the watcher. Note that there is no C<loop> argument, as the |
2714 | constructor already stores the event loop. |
3543 | constructor already stores the event loop. |
2715 | |
3544 | |
|
|
3545 | =item w->start ([arguments]) |
|
|
3546 | |
|
|
3547 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3548 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3549 | the configure C<set> method of the watcher. |
|
|
3550 | |
2716 | =item w->stop () |
3551 | =item w->stop () |
2717 | |
3552 | |
2718 | Stops the watcher if it is active. Again, no C<loop> argument. |
3553 | Stops the watcher if it is active. Again, no C<loop> argument. |
2719 | |
3554 | |
2720 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3555 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2732 | |
3567 | |
2733 | =back |
3568 | =back |
2734 | |
3569 | |
2735 | =back |
3570 | =back |
2736 | |
3571 | |
2737 | Example: Define a class with an IO and idle watcher, start one of them in |
3572 | Example: Define a class with two I/O and idle watchers, start the I/O |
2738 | the constructor. |
3573 | watchers in the constructor. |
2739 | |
3574 | |
2740 | class myclass |
3575 | class myclass |
2741 | { |
3576 | { |
2742 | ev::io io ; void io_cb (ev::io &w, int revents); |
3577 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3578 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2743 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3579 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2744 | |
3580 | |
2745 | myclass (int fd) |
3581 | myclass (int fd) |
2746 | { |
3582 | { |
2747 | io .set <myclass, &myclass::io_cb > (this); |
3583 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3584 | io2 .set <myclass, &myclass::io2_cb > (this); |
2748 | idle.set <myclass, &myclass::idle_cb> (this); |
3585 | idle.set <myclass, &myclass::idle_cb> (this); |
2749 | |
3586 | |
2750 | io.start (fd, ev::READ); |
3587 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3588 | io.start (); // start it whenever convenient |
|
|
3589 | |
|
|
3590 | io2.start (fd, ev::READ); // set + start in one call |
2751 | } |
3591 | } |
2752 | }; |
3592 | }; |
2753 | |
3593 | |
2754 | |
3594 | |
2755 | =head1 OTHER LANGUAGE BINDINGS |
3595 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2774 | L<http://software.schmorp.de/pkg/EV>. |
3614 | L<http://software.schmorp.de/pkg/EV>. |
2775 | |
3615 | |
2776 | =item Python |
3616 | =item Python |
2777 | |
3617 | |
2778 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3618 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2779 | seems to be quite complete and well-documented. Note, however, that the |
3619 | seems to be quite complete and well-documented. |
2780 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2781 | for everybody else, and therefore, should never be applied in an installed |
|
|
2782 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2783 | libev). |
|
|
2784 | |
3620 | |
2785 | =item Ruby |
3621 | =item Ruby |
2786 | |
3622 | |
2787 | Tony Arcieri has written a ruby extension that offers access to a subset |
3623 | Tony Arcieri has written a ruby extension that offers access to a subset |
2788 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3624 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2789 | more on top of it. It can be found via gem servers. Its homepage is at |
3625 | more on top of it. It can be found via gem servers. Its homepage is at |
2790 | L<http://rev.rubyforge.org/>. |
3626 | L<http://rev.rubyforge.org/>. |
2791 | |
3627 | |
|
|
3628 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3629 | makes rev work even on mingw. |
|
|
3630 | |
|
|
3631 | =item Haskell |
|
|
3632 | |
|
|
3633 | A haskell binding to libev is available at |
|
|
3634 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3635 | |
2792 | =item D |
3636 | =item D |
2793 | |
3637 | |
2794 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3638 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2795 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3639 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3640 | |
|
|
3641 | =item Ocaml |
|
|
3642 | |
|
|
3643 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3644 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3645 | |
|
|
3646 | =item Lua |
|
|
3647 | |
|
|
3648 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3649 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3650 | L<http://github.com/brimworks/lua-ev>. |
2796 | |
3651 | |
2797 | =back |
3652 | =back |
2798 | |
3653 | |
2799 | |
3654 | |
2800 | =head1 MACRO MAGIC |
3655 | =head1 MACRO MAGIC |
… | |
… | |
2814 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3669 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2815 | C<EV_A_> is used when other arguments are following. Example: |
3670 | C<EV_A_> is used when other arguments are following. Example: |
2816 | |
3671 | |
2817 | ev_unref (EV_A); |
3672 | ev_unref (EV_A); |
2818 | ev_timer_add (EV_A_ watcher); |
3673 | ev_timer_add (EV_A_ watcher); |
2819 | ev_loop (EV_A_ 0); |
3674 | ev_run (EV_A_ 0); |
2820 | |
3675 | |
2821 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3676 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2822 | which is often provided by the following macro. |
3677 | which is often provided by the following macro. |
2823 | |
3678 | |
2824 | =item C<EV_P>, C<EV_P_> |
3679 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
2864 | } |
3719 | } |
2865 | |
3720 | |
2866 | ev_check check; |
3721 | ev_check check; |
2867 | ev_check_init (&check, check_cb); |
3722 | ev_check_init (&check, check_cb); |
2868 | ev_check_start (EV_DEFAULT_ &check); |
3723 | ev_check_start (EV_DEFAULT_ &check); |
2869 | ev_loop (EV_DEFAULT_ 0); |
3724 | ev_run (EV_DEFAULT_ 0); |
2870 | |
3725 | |
2871 | =head1 EMBEDDING |
3726 | =head1 EMBEDDING |
2872 | |
3727 | |
2873 | Libev can (and often is) directly embedded into host |
3728 | Libev can (and often is) directly embedded into host |
2874 | applications. Examples of applications that embed it include the Deliantra |
3729 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2901 | |
3756 | |
2902 | #define EV_STANDALONE 1 |
3757 | #define EV_STANDALONE 1 |
2903 | #include "ev.h" |
3758 | #include "ev.h" |
2904 | |
3759 | |
2905 | Both header files and implementation files can be compiled with a C++ |
3760 | Both header files and implementation files can be compiled with a C++ |
2906 | compiler (at least, thats a stated goal, and breakage will be treated |
3761 | compiler (at least, that's a stated goal, and breakage will be treated |
2907 | as a bug). |
3762 | as a bug). |
2908 | |
3763 | |
2909 | You need the following files in your source tree, or in a directory |
3764 | You need the following files in your source tree, or in a directory |
2910 | in your include path (e.g. in libev/ when using -Ilibev): |
3765 | in your include path (e.g. in libev/ when using -Ilibev): |
2911 | |
3766 | |
… | |
… | |
2954 | libev.m4 |
3809 | libev.m4 |
2955 | |
3810 | |
2956 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3811 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2957 | |
3812 | |
2958 | Libev can be configured via a variety of preprocessor symbols you have to |
3813 | Libev can be configured via a variety of preprocessor symbols you have to |
2959 | define before including any of its files. The default in the absence of |
3814 | define before including (or compiling) any of its files. The default in |
2960 | autoconf is documented for every option. |
3815 | the absence of autoconf is documented for every option. |
|
|
3816 | |
|
|
3817 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3818 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3819 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3820 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3821 | users of libev and the libev code itself must be compiled with compatible |
|
|
3822 | settings. |
2961 | |
3823 | |
2962 | =over 4 |
3824 | =over 4 |
2963 | |
3825 | |
|
|
3826 | =item EV_COMPAT3 (h) |
|
|
3827 | |
|
|
3828 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3829 | release of libev comes with wrappers for the functions and symbols that |
|
|
3830 | have been renamed between libev version 3 and 4. |
|
|
3831 | |
|
|
3832 | You can disable these wrappers (to test compatibility with future |
|
|
3833 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3834 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3835 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3836 | typedef in that case. |
|
|
3837 | |
|
|
3838 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3839 | and in some even more future version the compatibility code will be |
|
|
3840 | removed completely. |
|
|
3841 | |
2964 | =item EV_STANDALONE |
3842 | =item EV_STANDALONE (h) |
2965 | |
3843 | |
2966 | Must always be C<1> if you do not use autoconf configuration, which |
3844 | Must always be C<1> if you do not use autoconf configuration, which |
2967 | keeps libev from including F<config.h>, and it also defines dummy |
3845 | keeps libev from including F<config.h>, and it also defines dummy |
2968 | implementations for some libevent functions (such as logging, which is not |
3846 | implementations for some libevent functions (such as logging, which is not |
2969 | supported). It will also not define any of the structs usually found in |
3847 | supported). It will also not define any of the structs usually found in |
2970 | F<event.h> that are not directly supported by the libev core alone. |
3848 | F<event.h> that are not directly supported by the libev core alone. |
2971 | |
3849 | |
|
|
3850 | In standalone mode, libev will still try to automatically deduce the |
|
|
3851 | configuration, but has to be more conservative. |
|
|
3852 | |
2972 | =item EV_USE_MONOTONIC |
3853 | =item EV_USE_MONOTONIC |
2973 | |
3854 | |
2974 | If defined to be C<1>, libev will try to detect the availability of the |
3855 | If defined to be C<1>, libev will try to detect the availability of the |
2975 | monotonic clock option at both compile time and runtime. Otherwise no use |
3856 | monotonic clock option at both compile time and runtime. Otherwise no |
2976 | of the monotonic clock option will be attempted. If you enable this, you |
3857 | use of the monotonic clock option will be attempted. If you enable this, |
2977 | usually have to link against librt or something similar. Enabling it when |
3858 | you usually have to link against librt or something similar. Enabling it |
2978 | the functionality isn't available is safe, though, although you have |
3859 | when the functionality isn't available is safe, though, although you have |
2979 | to make sure you link against any libraries where the C<clock_gettime> |
3860 | to make sure you link against any libraries where the C<clock_gettime> |
2980 | function is hiding in (often F<-lrt>). |
3861 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2981 | |
3862 | |
2982 | =item EV_USE_REALTIME |
3863 | =item EV_USE_REALTIME |
2983 | |
3864 | |
2984 | If defined to be C<1>, libev will try to detect the availability of the |
3865 | If defined to be C<1>, libev will try to detect the availability of the |
2985 | real-time clock option at compile time (and assume its availability at |
3866 | real-time clock option at compile time (and assume its availability |
2986 | runtime if successful). Otherwise no use of the real-time clock option will |
3867 | at runtime if successful). Otherwise no use of the real-time clock |
2987 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3868 | option will be attempted. This effectively replaces C<gettimeofday> |
2988 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3869 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2989 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3870 | correctness. See the note about libraries in the description of |
|
|
3871 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3872 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3873 | |
|
|
3874 | =item EV_USE_CLOCK_SYSCALL |
|
|
3875 | |
|
|
3876 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3877 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3878 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3879 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3880 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3881 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3882 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3883 | higher, as it simplifies linking (no need for C<-lrt>). |
2990 | |
3884 | |
2991 | =item EV_USE_NANOSLEEP |
3885 | =item EV_USE_NANOSLEEP |
2992 | |
3886 | |
2993 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3887 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2994 | and will use it for delays. Otherwise it will use C<select ()>. |
3888 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3010 | |
3904 | |
3011 | =item EV_SELECT_USE_FD_SET |
3905 | =item EV_SELECT_USE_FD_SET |
3012 | |
3906 | |
3013 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3907 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3014 | structure. This is useful if libev doesn't compile due to a missing |
3908 | structure. This is useful if libev doesn't compile due to a missing |
3015 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3909 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3016 | exotic systems. This usually limits the range of file descriptors to some |
3910 | on exotic systems. This usually limits the range of file descriptors to |
3017 | low limit such as 1024 or might have other limitations (winsocket only |
3911 | some low limit such as 1024 or might have other limitations (winsocket |
3018 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3912 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3019 | influence the size of the C<fd_set> used. |
3913 | configures the maximum size of the C<fd_set>. |
3020 | |
3914 | |
3021 | =item EV_SELECT_IS_WINSOCKET |
3915 | =item EV_SELECT_IS_WINSOCKET |
3022 | |
3916 | |
3023 | When defined to C<1>, the select backend will assume that |
3917 | When defined to C<1>, the select backend will assume that |
3024 | select/socket/connect etc. don't understand file descriptors but |
3918 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3026 | be used is the winsock select). This means that it will call |
3920 | be used is the winsock select). This means that it will call |
3027 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3921 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3028 | it is assumed that all these functions actually work on fds, even |
3922 | it is assumed that all these functions actually work on fds, even |
3029 | on win32. Should not be defined on non-win32 platforms. |
3923 | on win32. Should not be defined on non-win32 platforms. |
3030 | |
3924 | |
3031 | =item EV_FD_TO_WIN32_HANDLE |
3925 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3032 | |
3926 | |
3033 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3927 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3034 | file descriptors to socket handles. When not defining this symbol (the |
3928 | file descriptors to socket handles. When not defining this symbol (the |
3035 | default), then libev will call C<_get_osfhandle>, which is usually |
3929 | default), then libev will call C<_get_osfhandle>, which is usually |
3036 | correct. In some cases, programs use their own file descriptor management, |
3930 | correct. In some cases, programs use their own file descriptor management, |
3037 | in which case they can provide this function to map fds to socket handles. |
3931 | in which case they can provide this function to map fds to socket handles. |
|
|
3932 | |
|
|
3933 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3934 | |
|
|
3935 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3936 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3937 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3938 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3939 | |
|
|
3940 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3941 | |
|
|
3942 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3943 | macro can be used to override the C<close> function, useful to unregister |
|
|
3944 | file descriptors again. Note that the replacement function has to close |
|
|
3945 | the underlying OS handle. |
3038 | |
3946 | |
3039 | =item EV_USE_POLL |
3947 | =item EV_USE_POLL |
3040 | |
3948 | |
3041 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3949 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3042 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3950 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3089 | as well as for signal and thread safety in C<ev_async> watchers. |
3997 | as well as for signal and thread safety in C<ev_async> watchers. |
3090 | |
3998 | |
3091 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3999 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3092 | (from F<signal.h>), which is usually good enough on most platforms. |
4000 | (from F<signal.h>), which is usually good enough on most platforms. |
3093 | |
4001 | |
3094 | =item EV_H |
4002 | =item EV_H (h) |
3095 | |
4003 | |
3096 | The name of the F<ev.h> header file used to include it. The default if |
4004 | The name of the F<ev.h> header file used to include it. The default if |
3097 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4005 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3098 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4006 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3099 | |
4007 | |
3100 | =item EV_CONFIG_H |
4008 | =item EV_CONFIG_H (h) |
3101 | |
4009 | |
3102 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4010 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3103 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4011 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3104 | C<EV_H>, above. |
4012 | C<EV_H>, above. |
3105 | |
4013 | |
3106 | =item EV_EVENT_H |
4014 | =item EV_EVENT_H (h) |
3107 | |
4015 | |
3108 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4016 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3109 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4017 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3110 | |
4018 | |
3111 | =item EV_PROTOTYPES |
4019 | =item EV_PROTOTYPES (h) |
3112 | |
4020 | |
3113 | If defined to be C<0>, then F<ev.h> will not define any function |
4021 | If defined to be C<0>, then F<ev.h> will not define any function |
3114 | prototypes, but still define all the structs and other symbols. This is |
4022 | prototypes, but still define all the structs and other symbols. This is |
3115 | occasionally useful if you want to provide your own wrapper functions |
4023 | occasionally useful if you want to provide your own wrapper functions |
3116 | around libev functions. |
4024 | around libev functions. |
… | |
… | |
3138 | fine. |
4046 | fine. |
3139 | |
4047 | |
3140 | If your embedding application does not need any priorities, defining these |
4048 | If your embedding application does not need any priorities, defining these |
3141 | both to C<0> will save some memory and CPU. |
4049 | both to C<0> will save some memory and CPU. |
3142 | |
4050 | |
3143 | =item EV_PERIODIC_ENABLE |
4051 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4052 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4053 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3144 | |
4054 | |
3145 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4055 | If undefined or defined to be C<1> (and the platform supports it), then |
3146 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4056 | the respective watcher type is supported. If defined to be C<0>, then it |
3147 | code. |
4057 | is not. Disabling watcher types mainly saves code size. |
3148 | |
4058 | |
3149 | =item EV_IDLE_ENABLE |
4059 | =item EV_FEATURES |
3150 | |
|
|
3151 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3152 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3153 | code. |
|
|
3154 | |
|
|
3155 | =item EV_EMBED_ENABLE |
|
|
3156 | |
|
|
3157 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3158 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3159 | watcher types, which therefore must not be disabled. |
|
|
3160 | |
|
|
3161 | =item EV_STAT_ENABLE |
|
|
3162 | |
|
|
3163 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3164 | defined to be C<0>, then they are not. |
|
|
3165 | |
|
|
3166 | =item EV_FORK_ENABLE |
|
|
3167 | |
|
|
3168 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3169 | defined to be C<0>, then they are not. |
|
|
3170 | |
|
|
3171 | =item EV_ASYNC_ENABLE |
|
|
3172 | |
|
|
3173 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3174 | defined to be C<0>, then they are not. |
|
|
3175 | |
|
|
3176 | =item EV_MINIMAL |
|
|
3177 | |
4060 | |
3178 | If you need to shave off some kilobytes of code at the expense of some |
4061 | If you need to shave off some kilobytes of code at the expense of some |
3179 | speed, define this symbol to C<1>. Currently this is used to override some |
4062 | speed (but with the full API), you can define this symbol to request |
3180 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4063 | certain subsets of functionality. The default is to enable all features |
3181 | much smaller 2-heap for timer management over the default 4-heap. |
4064 | that can be enabled on the platform. |
|
|
4065 | |
|
|
4066 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4067 | with some broad features you want) and then selectively re-enable |
|
|
4068 | additional parts you want, for example if you want everything minimal, |
|
|
4069 | but multiple event loop support, async and child watchers and the poll |
|
|
4070 | backend, use this: |
|
|
4071 | |
|
|
4072 | #define EV_FEATURES 0 |
|
|
4073 | #define EV_MULTIPLICITY 1 |
|
|
4074 | #define EV_USE_POLL 1 |
|
|
4075 | #define EV_CHILD_ENABLE 1 |
|
|
4076 | #define EV_ASYNC_ENABLE 1 |
|
|
4077 | |
|
|
4078 | The actual value is a bitset, it can be a combination of the following |
|
|
4079 | values: |
|
|
4080 | |
|
|
4081 | =over 4 |
|
|
4082 | |
|
|
4083 | =item C<1> - faster/larger code |
|
|
4084 | |
|
|
4085 | Use larger code to speed up some operations. |
|
|
4086 | |
|
|
4087 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4088 | code size by roughly 30% on amd64). |
|
|
4089 | |
|
|
4090 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4091 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4092 | assertions. |
|
|
4093 | |
|
|
4094 | =item C<2> - faster/larger data structures |
|
|
4095 | |
|
|
4096 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4097 | hash table sizes and so on. This will usually further increase code size |
|
|
4098 | and can additionally have an effect on the size of data structures at |
|
|
4099 | runtime. |
|
|
4100 | |
|
|
4101 | =item C<4> - full API configuration |
|
|
4102 | |
|
|
4103 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4104 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4105 | |
|
|
4106 | =item C<8> - full API |
|
|
4107 | |
|
|
4108 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4109 | details on which parts of the API are still available without this |
|
|
4110 | feature, and do not complain if this subset changes over time. |
|
|
4111 | |
|
|
4112 | =item C<16> - enable all optional watcher types |
|
|
4113 | |
|
|
4114 | Enables all optional watcher types. If you want to selectively enable |
|
|
4115 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4116 | embed, async, child...) you can enable them manually by defining |
|
|
4117 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4118 | |
|
|
4119 | =item C<32> - enable all backends |
|
|
4120 | |
|
|
4121 | This enables all backends - without this feature, you need to enable at |
|
|
4122 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4123 | |
|
|
4124 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4125 | |
|
|
4126 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4127 | default. |
|
|
4128 | |
|
|
4129 | =back |
|
|
4130 | |
|
|
4131 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4132 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4133 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4134 | watchers, timers and monotonic clock support. |
|
|
4135 | |
|
|
4136 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4137 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4138 | your program might be left out as well - a binary starting a timer and an |
|
|
4139 | I/O watcher then might come out at only 5Kb. |
|
|
4140 | |
|
|
4141 | =item EV_AVOID_STDIO |
|
|
4142 | |
|
|
4143 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4144 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4145 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4146 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4147 | big. |
|
|
4148 | |
|
|
4149 | Note that error messages might become less precise when this option is |
|
|
4150 | enabled. |
|
|
4151 | |
|
|
4152 | =item EV_NSIG |
|
|
4153 | |
|
|
4154 | The highest supported signal number, +1 (or, the number of |
|
|
4155 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4156 | automatically, but sometimes this fails, in which case it can be |
|
|
4157 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4158 | good for about any system in existence) can save some memory, as libev |
|
|
4159 | statically allocates some 12-24 bytes per signal number. |
3182 | |
4160 | |
3183 | =item EV_PID_HASHSIZE |
4161 | =item EV_PID_HASHSIZE |
3184 | |
4162 | |
3185 | C<ev_child> watchers use a small hash table to distribute workload by |
4163 | C<ev_child> watchers use a small hash table to distribute workload by |
3186 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4164 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3187 | than enough. If you need to manage thousands of children you might want to |
4165 | usually more than enough. If you need to manage thousands of children you |
3188 | increase this value (I<must> be a power of two). |
4166 | might want to increase this value (I<must> be a power of two). |
3189 | |
4167 | |
3190 | =item EV_INOTIFY_HASHSIZE |
4168 | =item EV_INOTIFY_HASHSIZE |
3191 | |
4169 | |
3192 | C<ev_stat> watchers use a small hash table to distribute workload by |
4170 | C<ev_stat> watchers use a small hash table to distribute workload by |
3193 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4171 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3194 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4172 | disabled), usually more than enough. If you need to manage thousands of |
3195 | watchers you might want to increase this value (I<must> be a power of |
4173 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3196 | two). |
4174 | power of two). |
3197 | |
4175 | |
3198 | =item EV_USE_4HEAP |
4176 | =item EV_USE_4HEAP |
3199 | |
4177 | |
3200 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4178 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3201 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4179 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3202 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4180 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3203 | faster performance with many (thousands) of watchers. |
4181 | faster performance with many (thousands) of watchers. |
3204 | |
4182 | |
3205 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4183 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3206 | (disabled). |
4184 | will be C<0>. |
3207 | |
4185 | |
3208 | =item EV_HEAP_CACHE_AT |
4186 | =item EV_HEAP_CACHE_AT |
3209 | |
4187 | |
3210 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4188 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3211 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4189 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3212 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4190 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3213 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4191 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3214 | but avoids random read accesses on heap changes. This improves performance |
4192 | but avoids random read accesses on heap changes. This improves performance |
3215 | noticeably with many (hundreds) of watchers. |
4193 | noticeably with many (hundreds) of watchers. |
3216 | |
4194 | |
3217 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4195 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3218 | (disabled). |
4196 | will be C<0>. |
3219 | |
4197 | |
3220 | =item EV_VERIFY |
4198 | =item EV_VERIFY |
3221 | |
4199 | |
3222 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4200 | Controls how much internal verification (see C<ev_verify ()>) will |
3223 | be done: If set to C<0>, no internal verification code will be compiled |
4201 | be done: If set to C<0>, no internal verification code will be compiled |
3224 | in. If set to C<1>, then verification code will be compiled in, but not |
4202 | in. If set to C<1>, then verification code will be compiled in, but not |
3225 | called. If set to C<2>, then the internal verification code will be |
4203 | called. If set to C<2>, then the internal verification code will be |
3226 | called once per loop, which can slow down libev. If set to C<3>, then the |
4204 | called once per loop, which can slow down libev. If set to C<3>, then the |
3227 | verification code will be called very frequently, which will slow down |
4205 | verification code will be called very frequently, which will slow down |
3228 | libev considerably. |
4206 | libev considerably. |
3229 | |
4207 | |
3230 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4208 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3231 | C<0>. |
4209 | will be C<0>. |
3232 | |
4210 | |
3233 | =item EV_COMMON |
4211 | =item EV_COMMON |
3234 | |
4212 | |
3235 | By default, all watchers have a C<void *data> member. By redefining |
4213 | By default, all watchers have a C<void *data> member. By redefining |
3236 | this macro to a something else you can include more and other types of |
4214 | this macro to something else you can include more and other types of |
3237 | members. You have to define it each time you include one of the files, |
4215 | members. You have to define it each time you include one of the files, |
3238 | though, and it must be identical each time. |
4216 | though, and it must be identical each time. |
3239 | |
4217 | |
3240 | For example, the perl EV module uses something like this: |
4218 | For example, the perl EV module uses something like this: |
3241 | |
4219 | |
… | |
… | |
3294 | file. |
4272 | file. |
3295 | |
4273 | |
3296 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4274 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3297 | that everybody includes and which overrides some configure choices: |
4275 | that everybody includes and which overrides some configure choices: |
3298 | |
4276 | |
3299 | #define EV_MINIMAL 1 |
4277 | #define EV_FEATURES 8 |
3300 | #define EV_USE_POLL 0 |
4278 | #define EV_USE_SELECT 1 |
3301 | #define EV_MULTIPLICITY 0 |
|
|
3302 | #define EV_PERIODIC_ENABLE 0 |
4279 | #define EV_PREPARE_ENABLE 1 |
|
|
4280 | #define EV_IDLE_ENABLE 1 |
3303 | #define EV_STAT_ENABLE 0 |
4281 | #define EV_SIGNAL_ENABLE 1 |
3304 | #define EV_FORK_ENABLE 0 |
4282 | #define EV_CHILD_ENABLE 1 |
|
|
4283 | #define EV_USE_STDEXCEPT 0 |
3305 | #define EV_CONFIG_H <config.h> |
4284 | #define EV_CONFIG_H <config.h> |
3306 | #define EV_MINPRI 0 |
|
|
3307 | #define EV_MAXPRI 0 |
|
|
3308 | |
4285 | |
3309 | #include "ev++.h" |
4286 | #include "ev++.h" |
3310 | |
4287 | |
3311 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4288 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3312 | |
4289 | |
… | |
… | |
3372 | default loop and triggering an C<ev_async> watcher from the default loop |
4349 | default loop and triggering an C<ev_async> watcher from the default loop |
3373 | watcher callback into the event loop interested in the signal. |
4350 | watcher callback into the event loop interested in the signal. |
3374 | |
4351 | |
3375 | =back |
4352 | =back |
3376 | |
4353 | |
|
|
4354 | =head4 THREAD LOCKING EXAMPLE |
|
|
4355 | |
|
|
4356 | Here is a fictitious example of how to run an event loop in a different |
|
|
4357 | thread than where callbacks are being invoked and watchers are |
|
|
4358 | created/added/removed. |
|
|
4359 | |
|
|
4360 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4361 | which uses exactly this technique (which is suited for many high-level |
|
|
4362 | languages). |
|
|
4363 | |
|
|
4364 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4365 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4366 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4367 | |
|
|
4368 | First, you need to associate some data with the event loop: |
|
|
4369 | |
|
|
4370 | typedef struct { |
|
|
4371 | mutex_t lock; /* global loop lock */ |
|
|
4372 | ev_async async_w; |
|
|
4373 | thread_t tid; |
|
|
4374 | cond_t invoke_cv; |
|
|
4375 | } userdata; |
|
|
4376 | |
|
|
4377 | void prepare_loop (EV_P) |
|
|
4378 | { |
|
|
4379 | // for simplicity, we use a static userdata struct. |
|
|
4380 | static userdata u; |
|
|
4381 | |
|
|
4382 | ev_async_init (&u->async_w, async_cb); |
|
|
4383 | ev_async_start (EV_A_ &u->async_w); |
|
|
4384 | |
|
|
4385 | pthread_mutex_init (&u->lock, 0); |
|
|
4386 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4387 | |
|
|
4388 | // now associate this with the loop |
|
|
4389 | ev_set_userdata (EV_A_ u); |
|
|
4390 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4391 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4392 | |
|
|
4393 | // then create the thread running ev_loop |
|
|
4394 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4395 | } |
|
|
4396 | |
|
|
4397 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4398 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4399 | that might have been added: |
|
|
4400 | |
|
|
4401 | static void |
|
|
4402 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4403 | { |
|
|
4404 | // just used for the side effects |
|
|
4405 | } |
|
|
4406 | |
|
|
4407 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4408 | protecting the loop data, respectively. |
|
|
4409 | |
|
|
4410 | static void |
|
|
4411 | l_release (EV_P) |
|
|
4412 | { |
|
|
4413 | userdata *u = ev_userdata (EV_A); |
|
|
4414 | pthread_mutex_unlock (&u->lock); |
|
|
4415 | } |
|
|
4416 | |
|
|
4417 | static void |
|
|
4418 | l_acquire (EV_P) |
|
|
4419 | { |
|
|
4420 | userdata *u = ev_userdata (EV_A); |
|
|
4421 | pthread_mutex_lock (&u->lock); |
|
|
4422 | } |
|
|
4423 | |
|
|
4424 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4425 | into C<ev_run>: |
|
|
4426 | |
|
|
4427 | void * |
|
|
4428 | l_run (void *thr_arg) |
|
|
4429 | { |
|
|
4430 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4431 | |
|
|
4432 | l_acquire (EV_A); |
|
|
4433 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4434 | ev_run (EV_A_ 0); |
|
|
4435 | l_release (EV_A); |
|
|
4436 | |
|
|
4437 | return 0; |
|
|
4438 | } |
|
|
4439 | |
|
|
4440 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4441 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4442 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4443 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4444 | and b) skipping inter-thread-communication when there are no pending |
|
|
4445 | watchers is very beneficial): |
|
|
4446 | |
|
|
4447 | static void |
|
|
4448 | l_invoke (EV_P) |
|
|
4449 | { |
|
|
4450 | userdata *u = ev_userdata (EV_A); |
|
|
4451 | |
|
|
4452 | while (ev_pending_count (EV_A)) |
|
|
4453 | { |
|
|
4454 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4455 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4456 | } |
|
|
4457 | } |
|
|
4458 | |
|
|
4459 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4460 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4461 | thread to continue: |
|
|
4462 | |
|
|
4463 | static void |
|
|
4464 | real_invoke_pending (EV_P) |
|
|
4465 | { |
|
|
4466 | userdata *u = ev_userdata (EV_A); |
|
|
4467 | |
|
|
4468 | pthread_mutex_lock (&u->lock); |
|
|
4469 | ev_invoke_pending (EV_A); |
|
|
4470 | pthread_cond_signal (&u->invoke_cv); |
|
|
4471 | pthread_mutex_unlock (&u->lock); |
|
|
4472 | } |
|
|
4473 | |
|
|
4474 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4475 | event loop, you will now have to lock: |
|
|
4476 | |
|
|
4477 | ev_timer timeout_watcher; |
|
|
4478 | userdata *u = ev_userdata (EV_A); |
|
|
4479 | |
|
|
4480 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4481 | |
|
|
4482 | pthread_mutex_lock (&u->lock); |
|
|
4483 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4484 | ev_async_send (EV_A_ &u->async_w); |
|
|
4485 | pthread_mutex_unlock (&u->lock); |
|
|
4486 | |
|
|
4487 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4488 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4489 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4490 | watchers in the next event loop iteration. |
|
|
4491 | |
3377 | =head3 COROUTINES |
4492 | =head3 COROUTINES |
3378 | |
4493 | |
3379 | Libev is very accommodating to coroutines ("cooperative threads"): |
4494 | Libev is very accommodating to coroutines ("cooperative threads"): |
3380 | libev fully supports nesting calls to its functions from different |
4495 | libev fully supports nesting calls to its functions from different |
3381 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4496 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3382 | different coroutines, and switch freely between both coroutines running the |
4497 | different coroutines, and switch freely between both coroutines running |
3383 | loop, as long as you don't confuse yourself). The only exception is that |
4498 | the loop, as long as you don't confuse yourself). The only exception is |
3384 | you must not do this from C<ev_periodic> reschedule callbacks. |
4499 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3385 | |
4500 | |
3386 | Care has been taken to ensure that libev does not keep local state inside |
4501 | Care has been taken to ensure that libev does not keep local state inside |
3387 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4502 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3388 | they do not clal any callbacks. |
4503 | they do not call any callbacks. |
3389 | |
4504 | |
3390 | =head2 COMPILER WARNINGS |
4505 | =head2 COMPILER WARNINGS |
3391 | |
4506 | |
3392 | Depending on your compiler and compiler settings, you might get no or a |
4507 | Depending on your compiler and compiler settings, you might get no or a |
3393 | lot of warnings when compiling libev code. Some people are apparently |
4508 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3403 | maintainable. |
4518 | maintainable. |
3404 | |
4519 | |
3405 | And of course, some compiler warnings are just plain stupid, or simply |
4520 | And of course, some compiler warnings are just plain stupid, or simply |
3406 | wrong (because they don't actually warn about the condition their message |
4521 | wrong (because they don't actually warn about the condition their message |
3407 | seems to warn about). For example, certain older gcc versions had some |
4522 | seems to warn about). For example, certain older gcc versions had some |
3408 | warnings that resulted an extreme number of false positives. These have |
4523 | warnings that resulted in an extreme number of false positives. These have |
3409 | been fixed, but some people still insist on making code warn-free with |
4524 | been fixed, but some people still insist on making code warn-free with |
3410 | such buggy versions. |
4525 | such buggy versions. |
3411 | |
4526 | |
3412 | While libev is written to generate as few warnings as possible, |
4527 | While libev is written to generate as few warnings as possible, |
3413 | "warn-free" code is not a goal, and it is recommended not to build libev |
4528 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3427 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4542 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3428 | ==2274== possibly lost: 0 bytes in 0 blocks. |
4543 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3429 | ==2274== still reachable: 256 bytes in 1 blocks. |
4544 | ==2274== still reachable: 256 bytes in 1 blocks. |
3430 | |
4545 | |
3431 | Then there is no memory leak, just as memory accounted to global variables |
4546 | Then there is no memory leak, just as memory accounted to global variables |
3432 | is not a memleak - the memory is still being refernced, and didn't leak. |
4547 | is not a memleak - the memory is still being referenced, and didn't leak. |
3433 | |
4548 | |
3434 | Similarly, under some circumstances, valgrind might report kernel bugs |
4549 | Similarly, under some circumstances, valgrind might report kernel bugs |
3435 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4550 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3436 | although an acceptable workaround has been found here), or it might be |
4551 | although an acceptable workaround has been found here), or it might be |
3437 | confused. |
4552 | confused. |
… | |
… | |
3449 | I suggest using suppression lists. |
4564 | I suggest using suppression lists. |
3450 | |
4565 | |
3451 | |
4566 | |
3452 | =head1 PORTABILITY NOTES |
4567 | =head1 PORTABILITY NOTES |
3453 | |
4568 | |
|
|
4569 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4570 | |
|
|
4571 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4572 | interfaces but I<disables> them by default. |
|
|
4573 | |
|
|
4574 | That means that libev compiled in the default environment doesn't support |
|
|
4575 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4576 | |
|
|
4577 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4578 | by enabling the large file API, which makes them incompatible with the |
|
|
4579 | standard libev compiled for their system. |
|
|
4580 | |
|
|
4581 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4582 | suddenly make it incompatible to the default compile time environment, |
|
|
4583 | i.e. all programs not using special compile switches. |
|
|
4584 | |
|
|
4585 | =head2 OS/X AND DARWIN BUGS |
|
|
4586 | |
|
|
4587 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4588 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4589 | OpenGL drivers. |
|
|
4590 | |
|
|
4591 | =head3 C<kqueue> is buggy |
|
|
4592 | |
|
|
4593 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4594 | only sockets, many support pipes. |
|
|
4595 | |
|
|
4596 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4597 | rotten platform, but of course you can still ask for it when creating a |
|
|
4598 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4599 | probably going to work well. |
|
|
4600 | |
|
|
4601 | =head3 C<poll> is buggy |
|
|
4602 | |
|
|
4603 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4604 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4605 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4606 | |
|
|
4607 | Libev tries to work around this by not using C<poll> by default on |
|
|
4608 | this rotten platform, but of course you can still ask for it when creating |
|
|
4609 | a loop. |
|
|
4610 | |
|
|
4611 | =head3 C<select> is buggy |
|
|
4612 | |
|
|
4613 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4614 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4615 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4616 | you use more. |
|
|
4617 | |
|
|
4618 | There is an undocumented "workaround" for this - defining |
|
|
4619 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4620 | work on OS/X. |
|
|
4621 | |
|
|
4622 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4623 | |
|
|
4624 | =head3 C<errno> reentrancy |
|
|
4625 | |
|
|
4626 | The default compile environment on Solaris is unfortunately so |
|
|
4627 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4628 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4629 | defined by default. A valid, if stupid, implementation choice. |
|
|
4630 | |
|
|
4631 | If you want to use libev in threaded environments you have to make sure |
|
|
4632 | it's compiled with C<_REENTRANT> defined. |
|
|
4633 | |
|
|
4634 | =head3 Event port backend |
|
|
4635 | |
|
|
4636 | The scalable event interface for Solaris is called "event |
|
|
4637 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4638 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4639 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4640 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4641 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4642 | great. |
|
|
4643 | |
|
|
4644 | If you can't get it to work, you can try running the program by setting |
|
|
4645 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4646 | C<select> backends. |
|
|
4647 | |
|
|
4648 | =head2 AIX POLL BUG |
|
|
4649 | |
|
|
4650 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4651 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4652 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4653 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4654 | |
3454 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4655 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4656 | |
|
|
4657 | =head3 General issues |
3455 | |
4658 | |
3456 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4659 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3457 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4660 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3458 | model. Libev still offers limited functionality on this platform in |
4661 | model. Libev still offers limited functionality on this platform in |
3459 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4662 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3460 | descriptors. This only applies when using Win32 natively, not when using |
4663 | descriptors. This only applies when using Win32 natively, not when using |
3461 | e.g. cygwin. |
4664 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4665 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4666 | environment. |
3462 | |
4667 | |
3463 | Lifting these limitations would basically require the full |
4668 | Lifting these limitations would basically require the full |
3464 | re-implementation of the I/O system. If you are into these kinds of |
4669 | re-implementation of the I/O system. If you are into this kind of thing, |
3465 | things, then note that glib does exactly that for you in a very portable |
4670 | then note that glib does exactly that for you in a very portable way (note |
3466 | way (note also that glib is the slowest event library known to man). |
4671 | also that glib is the slowest event library known to man). |
3467 | |
4672 | |
3468 | There is no supported compilation method available on windows except |
4673 | There is no supported compilation method available on windows except |
3469 | embedding it into other applications. |
4674 | embedding it into other applications. |
|
|
4675 | |
|
|
4676 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4677 | tries its best, but under most conditions, signals will simply not work. |
3470 | |
4678 | |
3471 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4679 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3472 | accept large writes: instead of resulting in a partial write, windows will |
4680 | accept large writes: instead of resulting in a partial write, windows will |
3473 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4681 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3474 | so make sure you only write small amounts into your sockets (less than a |
4682 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3479 | the abysmal performance of winsockets, using a large number of sockets |
4687 | the abysmal performance of winsockets, using a large number of sockets |
3480 | is not recommended (and not reasonable). If your program needs to use |
4688 | is not recommended (and not reasonable). If your program needs to use |
3481 | more than a hundred or so sockets, then likely it needs to use a totally |
4689 | more than a hundred or so sockets, then likely it needs to use a totally |
3482 | different implementation for windows, as libev offers the POSIX readiness |
4690 | different implementation for windows, as libev offers the POSIX readiness |
3483 | notification model, which cannot be implemented efficiently on windows |
4691 | notification model, which cannot be implemented efficiently on windows |
3484 | (Microsoft monopoly games). |
4692 | (due to Microsoft monopoly games). |
3485 | |
4693 | |
3486 | A typical way to use libev under windows is to embed it (see the embedding |
4694 | A typical way to use libev under windows is to embed it (see the embedding |
3487 | section for details) and use the following F<evwrap.h> header file instead |
4695 | section for details) and use the following F<evwrap.h> header file instead |
3488 | of F<ev.h>: |
4696 | of F<ev.h>: |
3489 | |
4697 | |
… | |
… | |
3496 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4704 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3497 | |
4705 | |
3498 | #include "evwrap.h" |
4706 | #include "evwrap.h" |
3499 | #include "ev.c" |
4707 | #include "ev.c" |
3500 | |
4708 | |
3501 | =over 4 |
|
|
3502 | |
|
|
3503 | =item The winsocket select function |
4709 | =head3 The winsocket C<select> function |
3504 | |
4710 | |
3505 | The winsocket C<select> function doesn't follow POSIX in that it |
4711 | The winsocket C<select> function doesn't follow POSIX in that it |
3506 | requires socket I<handles> and not socket I<file descriptors> (it is |
4712 | requires socket I<handles> and not socket I<file descriptors> (it is |
3507 | also extremely buggy). This makes select very inefficient, and also |
4713 | also extremely buggy). This makes select very inefficient, and also |
3508 | requires a mapping from file descriptors to socket handles (the Microsoft |
4714 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3517 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4723 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3518 | |
4724 | |
3519 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4725 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3520 | complexity in the O(n²) range when using win32. |
4726 | complexity in the O(n²) range when using win32. |
3521 | |
4727 | |
3522 | =item Limited number of file descriptors |
4728 | =head3 Limited number of file descriptors |
3523 | |
4729 | |
3524 | Windows has numerous arbitrary (and low) limits on things. |
4730 | Windows has numerous arbitrary (and low) limits on things. |
3525 | |
4731 | |
3526 | Early versions of winsocket's select only supported waiting for a maximum |
4732 | Early versions of winsocket's select only supported waiting for a maximum |
3527 | of C<64> handles (probably owning to the fact that all windows kernels |
4733 | of C<64> handles (probably owning to the fact that all windows kernels |
3528 | can only wait for C<64> things at the same time internally; Microsoft |
4734 | can only wait for C<64> things at the same time internally; Microsoft |
3529 | recommends spawning a chain of threads and wait for 63 handles and the |
4735 | recommends spawning a chain of threads and wait for 63 handles and the |
3530 | previous thread in each. Great). |
4736 | previous thread in each. Sounds great!). |
3531 | |
4737 | |
3532 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4738 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3533 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4739 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3534 | call (which might be in libev or elsewhere, for example, perl does its own |
4740 | call (which might be in libev or elsewhere, for example, perl and many |
3535 | select emulation on windows). |
4741 | other interpreters do their own select emulation on windows). |
3536 | |
4742 | |
3537 | Another limit is the number of file descriptors in the Microsoft runtime |
4743 | Another limit is the number of file descriptors in the Microsoft runtime |
3538 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4744 | libraries, which by default is C<64> (there must be a hidden I<64> |
3539 | or something like this inside Microsoft). You can increase this by calling |
4745 | fetish or something like this inside Microsoft). You can increase this |
3540 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4746 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3541 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4747 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3542 | libraries. |
|
|
3543 | |
|
|
3544 | This might get you to about C<512> or C<2048> sockets (depending on |
4748 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3545 | windows version and/or the phase of the moon). To get more, you need to |
4749 | (depending on windows version and/or the phase of the moon). To get more, |
3546 | wrap all I/O functions and provide your own fd management, but the cost of |
4750 | you need to wrap all I/O functions and provide your own fd management, but |
3547 | calling select (O(n²)) will likely make this unworkable. |
4751 | the cost of calling select (O(n²)) will likely make this unworkable. |
3548 | |
|
|
3549 | =back |
|
|
3550 | |
4752 | |
3551 | =head2 PORTABILITY REQUIREMENTS |
4753 | =head2 PORTABILITY REQUIREMENTS |
3552 | |
4754 | |
3553 | In addition to a working ISO-C implementation and of course the |
4755 | In addition to a working ISO-C implementation and of course the |
3554 | backend-specific APIs, libev relies on a few additional extensions: |
4756 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
3561 | Libev assumes not only that all watcher pointers have the same internal |
4763 | Libev assumes not only that all watcher pointers have the same internal |
3562 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4764 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
3563 | assumes that the same (machine) code can be used to call any watcher |
4765 | assumes that the same (machine) code can be used to call any watcher |
3564 | callback: The watcher callbacks have different type signatures, but libev |
4766 | callback: The watcher callbacks have different type signatures, but libev |
3565 | calls them using an C<ev_watcher *> internally. |
4767 | calls them using an C<ev_watcher *> internally. |
|
|
4768 | |
|
|
4769 | =item pointer accesses must be thread-atomic |
|
|
4770 | |
|
|
4771 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4772 | writable in one piece - this is the case on all current architectures. |
3566 | |
4773 | |
3567 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4774 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3568 | |
4775 | |
3569 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4776 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3570 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4777 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
3593 | watchers. |
4800 | watchers. |
3594 | |
4801 | |
3595 | =item C<double> must hold a time value in seconds with enough accuracy |
4802 | =item C<double> must hold a time value in seconds with enough accuracy |
3596 | |
4803 | |
3597 | The type C<double> is used to represent timestamps. It is required to |
4804 | The type C<double> is used to represent timestamps. It is required to |
3598 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4805 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3599 | enough for at least into the year 4000. This requirement is fulfilled by |
4806 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4807 | (the design goal for libev). This requirement is overfulfilled by |
3600 | implementations implementing IEEE 754 (basically all existing ones). |
4808 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4809 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3601 | |
4810 | |
3602 | =back |
4811 | =back |
3603 | |
4812 | |
3604 | If you know of other additional requirements drop me a note. |
4813 | If you know of other additional requirements drop me a note. |
3605 | |
4814 | |
… | |
… | |
3673 | involves iterating over all running async watchers or all signal numbers. |
4882 | involves iterating over all running async watchers or all signal numbers. |
3674 | |
4883 | |
3675 | =back |
4884 | =back |
3676 | |
4885 | |
3677 | |
4886 | |
|
|
4887 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4888 | |
|
|
4889 | The major version 4 introduced some incompatible changes to the API. |
|
|
4890 | |
|
|
4891 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
4892 | for all changes, so most programs should still compile. The compatibility |
|
|
4893 | layer might be removed in later versions of libev, so better update to the |
|
|
4894 | new API early than late. |
|
|
4895 | |
|
|
4896 | =over 4 |
|
|
4897 | |
|
|
4898 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4899 | |
|
|
4900 | The backward compatibility mechanism can be controlled by |
|
|
4901 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4902 | section. |
|
|
4903 | |
|
|
4904 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
4905 | |
|
|
4906 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
4907 | |
|
|
4908 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
4909 | ev_loop_fork (EV_DEFAULT); |
|
|
4910 | |
|
|
4911 | =item function/symbol renames |
|
|
4912 | |
|
|
4913 | A number of functions and symbols have been renamed: |
|
|
4914 | |
|
|
4915 | ev_loop => ev_run |
|
|
4916 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
4917 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
4918 | |
|
|
4919 | ev_unloop => ev_break |
|
|
4920 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
4921 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
4922 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
4923 | |
|
|
4924 | EV_TIMEOUT => EV_TIMER |
|
|
4925 | |
|
|
4926 | ev_loop_count => ev_iteration |
|
|
4927 | ev_loop_depth => ev_depth |
|
|
4928 | ev_loop_verify => ev_verify |
|
|
4929 | |
|
|
4930 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4931 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
4932 | associated constants have been renamed to not collide with the C<struct |
|
|
4933 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
4934 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
4935 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
4936 | typedef. |
|
|
4937 | |
|
|
4938 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4939 | |
|
|
4940 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4941 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4942 | and work, but the library code will of course be larger. |
|
|
4943 | |
|
|
4944 | =back |
|
|
4945 | |
|
|
4946 | |
|
|
4947 | =head1 GLOSSARY |
|
|
4948 | |
|
|
4949 | =over 4 |
|
|
4950 | |
|
|
4951 | =item active |
|
|
4952 | |
|
|
4953 | A watcher is active as long as it has been started and not yet stopped. |
|
|
4954 | See L<WATCHER STATES> for details. |
|
|
4955 | |
|
|
4956 | =item application |
|
|
4957 | |
|
|
4958 | In this document, an application is whatever is using libev. |
|
|
4959 | |
|
|
4960 | =item backend |
|
|
4961 | |
|
|
4962 | The part of the code dealing with the operating system interfaces. |
|
|
4963 | |
|
|
4964 | =item callback |
|
|
4965 | |
|
|
4966 | The address of a function that is called when some event has been |
|
|
4967 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4968 | received the event, and the actual event bitset. |
|
|
4969 | |
|
|
4970 | =item callback/watcher invocation |
|
|
4971 | |
|
|
4972 | The act of calling the callback associated with a watcher. |
|
|
4973 | |
|
|
4974 | =item event |
|
|
4975 | |
|
|
4976 | A change of state of some external event, such as data now being available |
|
|
4977 | for reading on a file descriptor, time having passed or simply not having |
|
|
4978 | any other events happening anymore. |
|
|
4979 | |
|
|
4980 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4981 | C<EV_TIMER>). |
|
|
4982 | |
|
|
4983 | =item event library |
|
|
4984 | |
|
|
4985 | A software package implementing an event model and loop. |
|
|
4986 | |
|
|
4987 | =item event loop |
|
|
4988 | |
|
|
4989 | An entity that handles and processes external events and converts them |
|
|
4990 | into callback invocations. |
|
|
4991 | |
|
|
4992 | =item event model |
|
|
4993 | |
|
|
4994 | The model used to describe how an event loop handles and processes |
|
|
4995 | watchers and events. |
|
|
4996 | |
|
|
4997 | =item pending |
|
|
4998 | |
|
|
4999 | A watcher is pending as soon as the corresponding event has been |
|
|
5000 | detected. See L<WATCHER STATES> for details. |
|
|
5001 | |
|
|
5002 | =item real time |
|
|
5003 | |
|
|
5004 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5005 | |
|
|
5006 | =item wall-clock time |
|
|
5007 | |
|
|
5008 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5009 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
5010 | clock. |
|
|
5011 | |
|
|
5012 | =item watcher |
|
|
5013 | |
|
|
5014 | A data structure that describes interest in certain events. Watchers need |
|
|
5015 | to be started (attached to an event loop) before they can receive events. |
|
|
5016 | |
|
|
5017 | =back |
|
|
5018 | |
3678 | =head1 AUTHOR |
5019 | =head1 AUTHOR |
3679 | |
5020 | |
3680 | Marc Lehmann <libev@schmorp.de>. |
5021 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5022 | Magnusson and Emanuele Giaquinta. |
3681 | |
5023 | |