… | |
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26 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
27 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
28 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
29 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
30 | |
30 | |
31 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
33 | } |
33 | } |
34 | |
34 | |
35 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
36 | static void |
36 | static void |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
38 | { |
38 | { |
39 | puts ("timeout"); |
39 | puts ("timeout"); |
40 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
42 | } |
42 | } |
43 | |
43 | |
44 | int |
44 | int |
45 | main (void) |
45 | main (void) |
46 | { |
46 | { |
47 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
49 | |
50 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
52 | 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); |
53 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
56 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | 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 |
70 | 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 |
71 | 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 |
72 | |
92 | |
73 | 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 |
74 | 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 |
75 | these event sources and provide your program with events. |
95 | these event sources and provide your program with events. |
76 | |
96 | |
… | |
… | |
86 | =head2 FEATURES |
106 | =head2 FEATURES |
87 | |
107 | |
88 | 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 |
89 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
90 | 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 |
91 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
92 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
93 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
94 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
95 | 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 |
96 | 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 |
97 | (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>). |
98 | |
119 | |
99 | It also is quite fast (see this |
120 | It also is quite fast (see this |
100 | 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 |
101 | for example). |
122 | for example). |
102 | |
123 | |
… | |
… | |
105 | Libev is very configurable. In this manual the default (and most common) |
126 | Libev is very configurable. In this manual the default (and most common) |
106 | configuration will be described, which supports multiple event loops. For |
127 | configuration will be described, which supports multiple event loops. For |
107 | more info about various configuration options please have a look at |
128 | more info about various configuration options please have a look at |
108 | B<EMBED> section in this manual. If libev was configured without support |
129 | B<EMBED> section in this manual. If libev was configured without support |
109 | for multiple event loops, then all functions taking an initial argument of |
130 | for multiple event loops, then all functions taking an initial argument of |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
111 | this argument. |
132 | this argument. |
112 | |
133 | |
113 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
114 | |
135 | |
115 | Libev represents time as a single floating point number, representing the |
136 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
117 | 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 |
118 | 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 |
119 | 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 |
120 | 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 | |
121 | 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 |
122 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
123 | |
145 | |
124 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
125 | |
147 | |
126 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
127 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
151 | |
173 | |
152 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
153 | |
175 | |
154 | 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 |
155 | 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 |
156 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_now_update> and C<ev_now>. |
157 | |
180 | |
158 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
159 | |
182 | |
160 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
161 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
162 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
163 | |
192 | |
164 | =item int ev_version_major () |
193 | =item int ev_version_major () |
165 | |
194 | |
166 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
167 | |
196 | |
… | |
… | |
178 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
179 | compatible to older versions, so a larger minor version alone is usually |
208 | compatible to older versions, so a larger minor version alone is usually |
180 | not a problem. |
209 | not a problem. |
181 | |
210 | |
182 | Example: Make sure we haven't accidentally been linked against the wrong |
211 | Example: Make sure we haven't accidentally been linked against the wrong |
183 | version. |
212 | version (note, however, that this will not detect other ABI mismatches, |
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213 | such as LFS or reentrancy). |
184 | |
214 | |
185 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
186 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
187 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
188 | |
218 | |
… | |
… | |
199 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
200 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
201 | |
231 | |
202 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
203 | |
233 | |
204 | Return the set of all backends compiled into this binary of libev and also |
234 | Return the set of all backends compiled into this binary of libev and |
205 | recommended for this platform. This set is often smaller than the one |
235 | also recommended for this platform, meaning it will work for most file |
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236 | descriptor types. This set is often smaller than the one returned by |
206 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
237 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
207 | most BSDs and will not be auto-detected unless you explicitly request it |
238 | and will not be auto-detected unless you explicitly request it (assuming |
208 | (assuming you know what you are doing). This is the set of backends that |
239 | you know what you are doing). This is the set of backends that libev will |
209 | libev will probe for if you specify no backends explicitly. |
240 | probe for if you specify no backends explicitly. |
210 | |
241 | |
211 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
212 | |
243 | |
213 | Returns the set of backends that are embeddable in other event loops. This |
244 | Returns the set of backends that are embeddable in other event loops. This |
214 | is the theoretical, all-platform, value. To find which backends |
245 | value is platform-specific but can include backends not available on the |
215 | might be supported on the current system, you would need to look at |
246 | current system. To find which embeddable backends might be supported on |
216 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
217 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
218 | |
249 | |
219 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
220 | |
251 | |
221 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
222 | |
253 | |
223 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
224 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
225 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
226 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
252 | } |
283 | } |
253 | |
284 | |
254 | ... |
285 | ... |
255 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
256 | |
287 | |
257 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
258 | |
289 | |
259 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
260 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
261 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
262 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
274 | } |
305 | } |
275 | |
306 | |
276 | ... |
307 | ... |
277 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
278 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
279 | =back |
323 | =back |
280 | |
324 | |
281 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
282 | |
326 | |
283 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
284 | is I<not> optional in this case, as there is also an C<ev_loop> |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
285 | I<function>). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
286 | |
330 | |
287 | The library knows two types of such loops, the I<default> loop, which |
331 | The library knows two types of such loops, the I<default> loop, which |
288 | supports signals and child events, and dynamically created loops which do |
332 | supports child process events, and dynamically created event loops which |
289 | not. |
333 | do not. |
290 | |
334 | |
291 | =over 4 |
335 | =over 4 |
292 | |
336 | |
293 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
294 | |
338 | |
295 | This will initialise the default event loop if it hasn't been initialised |
339 | This returns the "default" event loop object, which is what you should |
296 | yet and return it. If the default loop could not be initialised, returns |
340 | normally use when you just need "the event loop". Event loop objects and |
297 | false. If it already was initialised it simply returns it (and ignores the |
341 | the C<flags> parameter are described in more detail in the entry for |
298 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
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343 | |
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344 | If the default loop is already initialised then this function simply |
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345 | returns it (and ignores the flags. If that is troubling you, check |
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346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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347 | flags, which should almost always be C<0>, unless the caller is also the |
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348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
299 | |
349 | |
300 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
301 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
302 | |
352 | |
303 | Note that this function is I<not> thread-safe, so if you want to use it |
353 | Note that this function is I<not> thread-safe, so if you want to use it |
304 | from multiple threads, you have to lock (note also that this is unlikely, |
354 | from multiple threads, you have to employ some kind of mutex (note also |
305 | as loops cannot be shared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
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356 | threads anyway). |
306 | |
357 | |
307 | The default loop is the only loop that can handle C<ev_signal> and |
358 | The default loop is the only loop that can handle C<ev_child> watchers, |
308 | C<ev_child> watchers, and to do this, it always registers a handler |
359 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
309 | for C<SIGCHLD>. If this is a problem for your application you can either |
360 | a problem for your application you can either create a dynamic loop with |
310 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
361 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
311 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
312 | C<ev_default_init>. |
363 | |
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364 | Example: This is the most typical usage. |
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365 | |
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366 | if (!ev_default_loop (0)) |
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367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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368 | |
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369 | Example: Restrict libev to the select and poll backends, and do not allow |
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370 | environment settings to be taken into account: |
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371 | |
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372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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373 | |
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374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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375 | |
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376 | This will create and initialise a new event loop object. If the loop |
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377 | could not be initialised, returns false. |
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378 | |
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379 | This function is thread-safe, and one common way to use libev with |
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380 | threads is indeed to create one loop per thread, and using the default |
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381 | loop in the "main" or "initial" thread. |
313 | |
382 | |
314 | The flags argument can be used to specify special behaviour or specific |
383 | The flags argument can be used to specify special behaviour or specific |
315 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
316 | |
385 | |
317 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
332 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, or to work |
333 | around bugs. |
402 | around bugs. |
334 | |
403 | |
335 | =item C<EVFLAG_FORKCHECK> |
404 | =item C<EVFLAG_FORKCHECK> |
336 | |
405 | |
337 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
338 | a fork, you can also make libev check for a fork in each iteration by |
407 | make libev check for a fork in each iteration by enabling this flag. |
339 | enabling this flag. |
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340 | |
408 | |
341 | This works by calling C<getpid ()> on every iteration of the loop, |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
342 | and thus this might slow down your event loop if you do a lot of loop |
410 | and thus this might slow down your event loop if you do a lot of loop |
343 | iterations and little real work, but is usually not noticeable (on my |
411 | iterations and little real work, but is usually not noticeable (on my |
344 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
350 | flag. |
418 | flag. |
351 | |
419 | |
352 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
353 | environment variable. |
421 | environment variable. |
354 | |
422 | |
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423 | =item C<EVFLAG_NOINOTIFY> |
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424 | |
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425 | When this flag is specified, then libev will not attempt to use the |
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426 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
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427 | testing, this flag can be useful to conserve inotify file descriptors, as |
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428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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429 | |
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430 | =item C<EVFLAG_SIGNALFD> |
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431 | |
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432 | When this flag is specified, then libev will attempt to use the |
|
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433 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
|
434 | delivers signals synchronously, which makes it both faster and might make |
|
|
435 | it possible to get the queued signal data. It can also simplify signal |
|
|
436 | handling with threads, as long as you properly block signals in your |
|
|
437 | threads that are not interested in handling them. |
|
|
438 | |
|
|
439 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
441 | example) that can't properly initialise their signal masks. |
|
|
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
|
444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
|
446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
447 | when you want to receive them. |
|
|
448 | |
|
|
449 | This behaviour is useful when you want to do your own signal handling, or |
|
|
450 | want to handle signals only in specific threads and want to avoid libev |
|
|
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
455 | |
|
|
456 | This flag's behaviour will become the default in future versions of libev. |
|
|
457 | |
355 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
356 | |
459 | |
357 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
358 | libev tries to roll its own fd_set with no limits on the number of fds, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
359 | but if that fails, expect a fairly low limit on the number of fds when |
462 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
383 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
384 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
385 | |
488 | |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
387 | |
490 | |
|
|
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
492 | kernels). |
|
|
493 | |
388 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
389 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
390 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
391 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
392 | |
498 | |
393 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
394 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
395 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
397 | so on. The biggest issue is fork races, however - if a program forks then |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
398 | I<both> parent and child process have to recreate the epoll set, which can |
506 | forks then I<both> parent and child process have to recreate the epoll |
399 | take considerable time (one syscall per file descriptor) and is of course |
507 | set, which can take considerable time (one syscall per file descriptor) |
400 | hard to detect. |
508 | and is of course hard to detect. |
401 | |
509 | |
402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
403 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
404 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
405 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
406 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
407 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
408 | events to filter out spurious ones, recreating the set when required. |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
520 | not least, it also refuses to work with some file descriptors which work |
|
|
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
522 | |
|
|
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
409 | |
526 | |
410 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
411 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
412 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
479 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
480 | |
597 | |
481 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
482 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
483 | |
600 | |
484 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
485 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
486 | blocking when no data (or space) is available. |
|
|
487 | |
|
|
488 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
489 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
490 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
491 | might perform better. |
604 | might perform better. |
492 | |
605 | |
493 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
494 | notifications, this backend actually performed fully to specification |
|
|
495 | in all tests and is fully embeddable, which is a rare feat among the |
607 | specification in all tests and is fully embeddable, which is a rare feat |
496 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
497 | |
620 | |
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
499 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
500 | |
623 | |
501 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
502 | |
625 | |
503 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
504 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
505 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
506 | |
629 | |
507 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
508 | |
639 | |
509 | =back |
640 | =back |
510 | |
641 | |
511 | If one or more of these are or'ed into the flags value, then only these |
642 | If one or more of the backend flags are or'ed into the flags value, |
512 | backends will be tried (in the reverse order as listed here). If none are |
643 | then only these backends will be tried (in the reverse order as listed |
513 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
514 | |
645 | ()> will be tried. |
515 | Example: This is the most typical usage. |
|
|
516 | |
|
|
517 | if (!ev_default_loop (0)) |
|
|
518 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
519 | |
|
|
520 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
521 | environment settings to be taken into account: |
|
|
522 | |
|
|
523 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
524 | |
|
|
525 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
526 | used if available (warning, breaks stuff, best use only with your own |
|
|
527 | private event loop and only if you know the OS supports your types of |
|
|
528 | fds): |
|
|
529 | |
|
|
530 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
531 | |
|
|
532 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
533 | |
|
|
534 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
535 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
536 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
537 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
538 | |
|
|
539 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
540 | libev with threads is indeed to create one loop per thread, and using the |
|
|
541 | default loop in the "main" or "initial" thread. |
|
|
542 | |
646 | |
543 | Example: Try to create a event loop that uses epoll and nothing else. |
647 | Example: Try to create a event loop that uses epoll and nothing else. |
544 | |
648 | |
545 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
546 | if (!epoller) |
650 | if (!epoller) |
547 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
548 | |
652 | |
|
|
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
654 | used if available. |
|
|
655 | |
|
|
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
657 | |
549 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
550 | |
659 | |
551 | Destroys the default loop again (frees all memory and kernel state |
660 | Destroys an event loop object (frees all memory and kernel state |
552 | etc.). None of the active event watchers will be stopped in the normal |
661 | etc.). None of the active event watchers will be stopped in the normal |
553 | sense, so e.g. C<ev_is_active> might still return true. It is your |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
554 | responsibility to either stop all watchers cleanly yourself I<before> |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
555 | calling this function, or cope with the fact afterwards (which is usually |
664 | calling this function, or cope with the fact afterwards (which is usually |
556 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
665 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
… | |
… | |
558 | |
667 | |
559 | Note that certain global state, such as signal state (and installed signal |
668 | Note that certain global state, such as signal state (and installed signal |
560 | handlers), will not be freed by this function, and related watchers (such |
669 | handlers), will not be freed by this function, and related watchers (such |
561 | as signal and child watchers) would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
562 | |
671 | |
563 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
564 | rare occasion where you really need to free e.g. the signal handling |
673 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
674 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
675 | |
|
|
676 | Note that it is not advisable to call this function on the default loop |
|
|
677 | except in the rare occasion where you really need to free its resources. |
565 | pipe fds. If you need dynamically allocated loops it is better to use |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
566 | C<ev_loop_new> and C<ev_loop_destroy>). |
679 | and C<ev_loop_destroy>. |
567 | |
680 | |
568 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
569 | |
682 | |
570 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
571 | earlier call to C<ev_loop_new>. |
|
|
572 | |
|
|
573 | =item ev_default_fork () |
|
|
574 | |
|
|
575 | This function sets a flag that causes subsequent C<ev_loop> iterations |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
576 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
577 | name, you can call it anytime, but it makes most sense after forking, in |
685 | name, you can call it anytime, but it makes most sense after forking, in |
578 | the child process (or both child and parent, but that again makes little |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
579 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
580 | functions, and it will only take effect at the next C<ev_loop> iteration. |
688 | |
|
|
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
692 | during fork. |
581 | |
693 | |
582 | On the other hand, you only need to call this function in the child |
694 | On the other hand, you only need to call this function in the child |
583 | process if and only if you want to use the event library in the child. If |
695 | process if and only if you want to use the event loop in the child. If |
584 | you just fork+exec, you don't have to call it at all. |
696 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
697 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
698 | difference, but libev will usually detect this case on its own and do a |
|
|
699 | costly reset of the backend). |
585 | |
700 | |
586 | The function itself is quite fast and it's usually not a problem to call |
701 | The function itself is quite fast and it's usually not a problem to call |
587 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
588 | quite nicely into a call to C<pthread_atfork>: |
|
|
589 | |
703 | |
|
|
704 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
705 | using pthreads. |
|
|
706 | |
|
|
707 | static void |
|
|
708 | post_fork_child (void) |
|
|
709 | { |
|
|
710 | ev_loop_fork (EV_DEFAULT); |
|
|
711 | } |
|
|
712 | |
|
|
713 | ... |
590 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
591 | |
|
|
592 | =item ev_loop_fork (loop) |
|
|
593 | |
|
|
594 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
595 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
596 | after fork that you want to re-use in the child, and how you do this is |
|
|
597 | entirely your own problem. |
|
|
598 | |
715 | |
599 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
600 | |
717 | |
601 | Returns true when the given loop is, in fact, the default loop, and false |
718 | Returns true when the given loop is, in fact, the default loop, and false |
602 | otherwise. |
719 | otherwise. |
603 | |
720 | |
604 | =item unsigned int ev_loop_count (loop) |
721 | =item unsigned int ev_iteration (loop) |
605 | |
722 | |
606 | Returns the count of loop iterations for the loop, which is identical to |
723 | Returns the current iteration count for the event loop, which is identical |
607 | the number of times libev did poll for new events. It starts at C<0> and |
724 | to the number of times libev did poll for new events. It starts at C<0> |
608 | happily wraps around with enough iterations. |
725 | and happily wraps around with enough iterations. |
609 | |
726 | |
610 | This value can sometimes be useful as a generation counter of sorts (it |
727 | This value can sometimes be useful as a generation counter of sorts (it |
611 | "ticks" the number of loop iterations), as it roughly corresponds with |
728 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
729 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
730 | prepare and check phases. |
|
|
731 | |
|
|
732 | =item unsigned int ev_depth (loop) |
|
|
733 | |
|
|
734 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
736 | |
|
|
737 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
739 | in which case it is higher. |
|
|
740 | |
|
|
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
613 | |
745 | |
614 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
615 | |
747 | |
616 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
617 | use. |
749 | use. |
… | |
… | |
626 | |
758 | |
627 | =item ev_now_update (loop) |
759 | =item ev_now_update (loop) |
628 | |
760 | |
629 | Establishes the current time by querying the kernel, updating the time |
761 | Establishes the current time by querying the kernel, updating the time |
630 | returned by C<ev_now ()> in the progress. This is a costly operation and |
762 | returned by C<ev_now ()> in the progress. This is a costly operation and |
631 | is usually done automatically within C<ev_loop ()>. |
763 | is usually done automatically within C<ev_run ()>. |
632 | |
764 | |
633 | This function is rarely useful, but when some event callback runs for a |
765 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
766 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
767 | the current time is a good idea. |
636 | |
768 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
638 | |
770 | |
|
|
771 | =item ev_suspend (loop) |
|
|
772 | |
|
|
773 | =item ev_resume (loop) |
|
|
774 | |
|
|
775 | These two functions suspend and resume an event loop, for use when the |
|
|
776 | loop is not used for a while and timeouts should not be processed. |
|
|
777 | |
|
|
778 | A typical use case would be an interactive program such as a game: When |
|
|
779 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
780 | would be best to handle timeouts as if no time had actually passed while |
|
|
781 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
782 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
783 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
784 | |
|
|
785 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
786 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
787 | will be rescheduled (that is, they will lose any events that would have |
|
|
788 | occurred while suspended). |
|
|
789 | |
|
|
790 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
791 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
792 | without a previous call to C<ev_suspend>. |
|
|
793 | |
|
|
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
795 | event loop time (see C<ev_now_update>). |
|
|
796 | |
639 | =item ev_loop (loop, int flags) |
797 | =item ev_run (loop, int flags) |
640 | |
798 | |
641 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
642 | after you initialised all your watchers and you want to start handling |
800 | after you have initialised all your watchers and you want to start |
643 | events. |
801 | handling events. It will ask the operating system for any new events, call |
|
|
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
803 | is why event loops are called I<loops>. |
644 | |
804 | |
645 | If the flags argument is specified as C<0>, it will not return until |
805 | If the flags argument is specified as C<0>, it will keep handling events |
646 | either no event watchers are active anymore or C<ev_unloop> was called. |
806 | until either no event watchers are active anymore or C<ev_break> was |
|
|
807 | called. |
647 | |
808 | |
648 | Please note that an explicit C<ev_unloop> is usually better than |
809 | Please note that an explicit C<ev_break> is usually better than |
649 | relying on all watchers to be stopped when deciding when a program has |
810 | relying on all watchers to be stopped when deciding when a program has |
650 | finished (especially in interactive programs), but having a program |
811 | finished (especially in interactive programs), but having a program |
651 | that automatically loops as long as it has to and no longer by virtue |
812 | that automatically loops as long as it has to and no longer by virtue |
652 | of relying on its watchers stopping correctly, that is truly a thing of |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
653 | beauty. |
814 | beauty. |
654 | |
815 | |
|
|
816 | This function is also I<mostly> exception-safe - you can break out of |
|
|
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
820 | |
655 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
656 | those events and any already outstanding ones, but will not block your |
822 | those events and any already outstanding ones, but will not wait and |
657 | process in case there are no events and will return after one iteration of |
823 | block your process in case there are no events and will return after one |
658 | the loop. |
824 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
825 | events while doing lengthy calculations, to keep the program responsive. |
659 | |
826 | |
660 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
827 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
661 | necessary) and will handle those and any already outstanding ones. It |
828 | necessary) and will handle those and any already outstanding ones. It |
662 | will block your process until at least one new event arrives (which could |
829 | will block your process until at least one new event arrives (which could |
663 | be an event internal to libev itself, so there is no guarantee that a |
830 | be an event internal to libev itself, so there is no guarantee that a |
664 | user-registered callback will be called), and will return after one |
831 | user-registered callback will be called), and will return after one |
665 | iteration of the loop. |
832 | iteration of the loop. |
666 | |
833 | |
667 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
668 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
669 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
670 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
671 | |
838 | |
672 | Here are the gory details of what C<ev_loop> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
673 | |
842 | |
|
|
843 | - Increment loop depth. |
|
|
844 | - Reset the ev_break status. |
674 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
|
|
846 | LOOP: |
675 | * If EVFLAG_FORKCHECK was used, check for a fork. |
847 | - If EVFLAG_FORKCHECK was used, check for a fork. |
676 | - If a fork was detected (by any means), queue and call all fork watchers. |
848 | - If a fork was detected (by any means), queue and call all fork watchers. |
677 | - Queue and call all prepare watchers. |
849 | - Queue and call all prepare watchers. |
|
|
850 | - If ev_break was called, goto FINISH. |
678 | - If we have been forked, detach and recreate the kernel state |
851 | - If we have been forked, detach and recreate the kernel state |
679 | as to not disturb the other process. |
852 | as to not disturb the other process. |
680 | - Update the kernel state with all outstanding changes. |
853 | - Update the kernel state with all outstanding changes. |
681 | - Update the "event loop time" (ev_now ()). |
854 | - Update the "event loop time" (ev_now ()). |
682 | - Calculate for how long to sleep or block, if at all |
855 | - Calculate for how long to sleep or block, if at all |
683 | (active idle watchers, EVLOOP_NONBLOCK or not having |
856 | (active idle watchers, EVRUN_NOWAIT or not having |
684 | any active watchers at all will result in not sleeping). |
857 | any active watchers at all will result in not sleeping). |
685 | - Sleep if the I/O and timer collect interval say so. |
858 | - Sleep if the I/O and timer collect interval say so. |
|
|
859 | - Increment loop iteration counter. |
686 | - Block the process, waiting for any events. |
860 | - Block the process, waiting for any events. |
687 | - Queue all outstanding I/O (fd) events. |
861 | - Queue all outstanding I/O (fd) events. |
688 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
862 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
689 | - Queue all expired timers. |
863 | - Queue all expired timers. |
690 | - Queue all expired periodics. |
864 | - Queue all expired periodics. |
691 | - Unless any events are pending now, queue all idle watchers. |
865 | - Queue all idle watchers with priority higher than that of pending events. |
692 | - Queue all check watchers. |
866 | - Queue all check watchers. |
693 | - Call all queued watchers in reverse order (i.e. check watchers first). |
867 | - Call all queued watchers in reverse order (i.e. check watchers first). |
694 | Signals and child watchers are implemented as I/O watchers, and will |
868 | Signals and child watchers are implemented as I/O watchers, and will |
695 | be handled here by queueing them when their watcher gets executed. |
869 | be handled here by queueing them when their watcher gets executed. |
696 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
870 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
697 | were used, or there are no active watchers, return, otherwise |
871 | were used, or there are no active watchers, goto FINISH, otherwise |
698 | continue with step *. |
872 | continue with step LOOP. |
|
|
873 | FINISH: |
|
|
874 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
875 | - Decrement the loop depth. |
|
|
876 | - Return. |
699 | |
877 | |
700 | Example: Queue some jobs and then loop until no events are outstanding |
878 | Example: Queue some jobs and then loop until no events are outstanding |
701 | anymore. |
879 | anymore. |
702 | |
880 | |
703 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
704 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
705 | ev_loop (my_loop, 0); |
883 | ev_run (my_loop, 0); |
706 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
707 | |
885 | |
708 | =item ev_unloop (loop, how) |
886 | =item ev_break (loop, how) |
709 | |
887 | |
710 | Can be used to make a call to C<ev_loop> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
711 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
712 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
890 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
713 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
891 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
714 | |
892 | |
715 | This "unloop state" will be cleared when entering C<ev_loop> again. |
893 | This "break state" will be cleared on the next call to C<ev_run>. |
716 | |
894 | |
717 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
895 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
896 | which case it will have no effect. |
718 | |
897 | |
719 | =item ev_ref (loop) |
898 | =item ev_ref (loop) |
720 | |
899 | |
721 | =item ev_unref (loop) |
900 | =item ev_unref (loop) |
722 | |
901 | |
723 | Ref/unref can be used to add or remove a reference count on the event |
902 | Ref/unref can be used to add or remove a reference count on the event |
724 | loop: Every watcher keeps one reference, and as long as the reference |
903 | loop: Every watcher keeps one reference, and as long as the reference |
725 | count is nonzero, C<ev_loop> will not return on its own. |
904 | count is nonzero, C<ev_run> will not return on its own. |
726 | |
905 | |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
906 | This is useful when you have a watcher that you never intend to |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
907 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
908 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
729 | stopping it. |
909 | before stopping it. |
730 | |
910 | |
731 | As an example, libev itself uses this for its internal signal pipe: It is |
911 | As an example, libev itself uses this for its internal signal pipe: It |
732 | not visible to the libev user and should not keep C<ev_loop> from exiting |
912 | is not visible to the libev user and should not keep C<ev_run> from |
733 | if no event watchers registered by it are active. It is also an excellent |
913 | exiting if no event watchers registered by it are active. It is also an |
734 | way to do this for generic recurring timers or from within third-party |
914 | excellent way to do this for generic recurring timers or from within |
735 | libraries. Just remember to I<unref after start> and I<ref before stop> |
915 | third-party libraries. Just remember to I<unref after start> and I<ref |
736 | (but only if the watcher wasn't active before, or was active before, |
916 | before stop> (but only if the watcher wasn't active before, or was active |
737 | respectively). |
917 | before, respectively. Note also that libev might stop watchers itself |
|
|
918 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
919 | in the callback). |
738 | |
920 | |
739 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
921 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
740 | running when nothing else is active. |
922 | running when nothing else is active. |
741 | |
923 | |
742 | ev_signal exitsig; |
924 | ev_signal exitsig; |
743 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
925 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
744 | ev_signal_start (loop, &exitsig); |
926 | ev_signal_start (loop, &exitsig); |
745 | evf_unref (loop); |
927 | ev_unref (loop); |
746 | |
928 | |
747 | Example: For some weird reason, unregister the above signal handler again. |
929 | Example: For some weird reason, unregister the above signal handler again. |
748 | |
930 | |
749 | ev_ref (loop); |
931 | ev_ref (loop); |
750 | ev_signal_stop (loop, &exitsig); |
932 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
770 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
771 | |
953 | |
772 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
773 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
774 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
775 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
776 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
959 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
777 | |
962 | |
778 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
779 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
780 | latency/jitter/inexactness (the watcher callback will be called |
965 | latency/jitter/inexactness (the watcher callback will be called |
781 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
783 | |
968 | |
784 | Many (busy) programs can usually benefit by setting the I/O collect |
969 | Many (busy) programs can usually benefit by setting the I/O collect |
785 | interval to a value near C<0.1> or so, which is often enough for |
970 | interval to a value near C<0.1> or so, which is often enough for |
786 | interactive servers (of course not for games), likewise for timeouts. It |
971 | interactive servers (of course not for games), likewise for timeouts. It |
787 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
972 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
788 | as this approaches the timing granularity of most systems. |
973 | as this approaches the timing granularity of most systems. Note that if |
|
|
974 | you do transactions with the outside world and you can't increase the |
|
|
975 | parallelity, then this setting will limit your transaction rate (if you |
|
|
976 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
977 | then you can't do more than 100 transactions per second). |
789 | |
978 | |
790 | Setting the I<timeout collect interval> can improve the opportunity for |
979 | Setting the I<timeout collect interval> can improve the opportunity for |
791 | saving power, as the program will "bundle" timer callback invocations that |
980 | saving power, as the program will "bundle" timer callback invocations that |
792 | are "near" in time together, by delaying some, thus reducing the number of |
981 | are "near" in time together, by delaying some, thus reducing the number of |
793 | times the process sleeps and wakes up again. Another useful technique to |
982 | times the process sleeps and wakes up again. Another useful technique to |
794 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
983 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
795 | they fire on, say, one-second boundaries only. |
984 | they fire on, say, one-second boundaries only. |
796 | |
985 | |
|
|
986 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
987 | more often than 100 times per second: |
|
|
988 | |
|
|
989 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
990 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
991 | |
|
|
992 | =item ev_invoke_pending (loop) |
|
|
993 | |
|
|
994 | This call will simply invoke all pending watchers while resetting their |
|
|
995 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
996 | but when overriding the invoke callback this call comes handy. This |
|
|
997 | function can be invoked from a watcher - this can be useful for example |
|
|
998 | when you want to do some lengthy calculation and want to pass further |
|
|
999 | event handling to another thread (you still have to make sure only one |
|
|
1000 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1001 | |
|
|
1002 | =item int ev_pending_count (loop) |
|
|
1003 | |
|
|
1004 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1005 | are pending. |
|
|
1006 | |
|
|
1007 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1008 | |
|
|
1009 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1010 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1011 | this callback instead. This is useful, for example, when you want to |
|
|
1012 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1013 | |
|
|
1014 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1015 | callback. |
|
|
1016 | |
|
|
1017 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
1018 | |
|
|
1019 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1021 | each call to a libev function. |
|
|
1022 | |
|
|
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1024 | to wait for it to return. One way around this is to wake up the event |
|
|
1025 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
1026 | I<release> and I<acquire> callbacks on the loop. |
|
|
1027 | |
|
|
1028 | When set, then C<release> will be called just before the thread is |
|
|
1029 | suspended waiting for new events, and C<acquire> is called just |
|
|
1030 | afterwards. |
|
|
1031 | |
|
|
1032 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1033 | C<acquire> will just call the mutex_lock function again. |
|
|
1034 | |
|
|
1035 | While event loop modifications are allowed between invocations of |
|
|
1036 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1037 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1038 | have no effect on the set of file descriptors being watched, or the time |
|
|
1039 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1040 | to take note of any changes you made. |
|
|
1041 | |
|
|
1042 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1043 | invocations of C<release> and C<acquire>. |
|
|
1044 | |
|
|
1045 | See also the locking example in the C<THREADS> section later in this |
|
|
1046 | document. |
|
|
1047 | |
|
|
1048 | =item ev_set_userdata (loop, void *data) |
|
|
1049 | |
|
|
1050 | =item void *ev_userdata (loop) |
|
|
1051 | |
|
|
1052 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1053 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1054 | C<0>. |
|
|
1055 | |
|
|
1056 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1057 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1058 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1059 | any other purpose as well. |
|
|
1060 | |
797 | =item ev_loop_verify (loop) |
1061 | =item ev_verify (loop) |
798 | |
1062 | |
799 | This function only does something when C<EV_VERIFY> support has been |
1063 | This function only does something when C<EV_VERIFY> support has been |
800 | compiled in, which is the default for non-minimal builds. It tries to go |
1064 | compiled in, which is the default for non-minimal builds. It tries to go |
801 | through all internal structures and checks them for validity. If anything |
1065 | through all internal structures and checks them for validity. If anything |
802 | is found to be inconsistent, it will print an error message to standard |
1066 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
813 | |
1077 | |
814 | In the following description, uppercase C<TYPE> in names stands for the |
1078 | In the following description, uppercase C<TYPE> in names stands for the |
815 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1079 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
816 | watchers and C<ev_io_start> for I/O watchers. |
1080 | watchers and C<ev_io_start> for I/O watchers. |
817 | |
1081 | |
818 | A watcher is a structure that you create and register to record your |
1082 | A watcher is an opaque structure that you allocate and register to record |
819 | interest in some event. For instance, if you want to wait for STDIN to |
1083 | your interest in some event. To make a concrete example, imagine you want |
820 | become readable, you would create an C<ev_io> watcher for that: |
1084 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1085 | for that: |
821 | |
1086 | |
822 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1087 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
823 | { |
1088 | { |
824 | ev_io_stop (w); |
1089 | ev_io_stop (w); |
825 | ev_unloop (loop, EVUNLOOP_ALL); |
1090 | ev_break (loop, EVBREAK_ALL); |
826 | } |
1091 | } |
827 | |
1092 | |
828 | struct ev_loop *loop = ev_default_loop (0); |
1093 | struct ev_loop *loop = ev_default_loop (0); |
829 | |
1094 | |
830 | ev_io stdin_watcher; |
1095 | ev_io stdin_watcher; |
831 | |
1096 | |
832 | ev_init (&stdin_watcher, my_cb); |
1097 | ev_init (&stdin_watcher, my_cb); |
833 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1098 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
834 | ev_io_start (loop, &stdin_watcher); |
1099 | ev_io_start (loop, &stdin_watcher); |
835 | |
1100 | |
836 | ev_loop (loop, 0); |
1101 | ev_run (loop, 0); |
837 | |
1102 | |
838 | As you can see, you are responsible for allocating the memory for your |
1103 | As you can see, you are responsible for allocating the memory for your |
839 | watcher structures (and it is I<usually> a bad idea to do this on the |
1104 | watcher structures (and it is I<usually> a bad idea to do this on the |
840 | stack). |
1105 | stack). |
841 | |
1106 | |
842 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1107 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
843 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1108 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
844 | |
1109 | |
845 | Each watcher structure must be initialised by a call to C<ev_init |
1110 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
846 | (watcher *, callback)>, which expects a callback to be provided. This |
1111 | *, callback)>, which expects a callback to be provided. This callback is |
847 | callback gets invoked each time the event occurs (or, in the case of I/O |
1112 | invoked each time the event occurs (or, in the case of I/O watchers, each |
848 | watchers, each time the event loop detects that the file descriptor given |
1113 | time the event loop detects that the file descriptor given is readable |
849 | is readable and/or writable). |
1114 | and/or writable). |
850 | |
1115 | |
851 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1116 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
852 | macro to configure it, with arguments specific to the watcher type. There |
1117 | macro to configure it, with arguments specific to the watcher type. There |
853 | is also a macro to combine initialisation and setting in one call: C<< |
1118 | is also a macro to combine initialisation and setting in one call: C<< |
854 | ev_TYPE_init (watcher *, callback, ...) >>. |
1119 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
877 | =item C<EV_WRITE> |
1142 | =item C<EV_WRITE> |
878 | |
1143 | |
879 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1144 | The file descriptor in the C<ev_io> watcher has become readable and/or |
880 | writable. |
1145 | writable. |
881 | |
1146 | |
882 | =item C<EV_TIMEOUT> |
1147 | =item C<EV_TIMER> |
883 | |
1148 | |
884 | The C<ev_timer> watcher has timed out. |
1149 | The C<ev_timer> watcher has timed out. |
885 | |
1150 | |
886 | =item C<EV_PERIODIC> |
1151 | =item C<EV_PERIODIC> |
887 | |
1152 | |
… | |
… | |
905 | |
1170 | |
906 | =item C<EV_PREPARE> |
1171 | =item C<EV_PREPARE> |
907 | |
1172 | |
908 | =item C<EV_CHECK> |
1173 | =item C<EV_CHECK> |
909 | |
1174 | |
910 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1175 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
911 | to gather new events, and all C<ev_check> watchers are invoked just after |
1176 | to gather new events, and all C<ev_check> watchers are invoked just after |
912 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1177 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
913 | received events. Callbacks of both watcher types can start and stop as |
1178 | received events. Callbacks of both watcher types can start and stop as |
914 | many watchers as they want, and all of them will be taken into account |
1179 | many watchers as they want, and all of them will be taken into account |
915 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1180 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
916 | C<ev_loop> from blocking). |
1181 | C<ev_run> from blocking). |
917 | |
1182 | |
918 | =item C<EV_EMBED> |
1183 | =item C<EV_EMBED> |
919 | |
1184 | |
920 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1185 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
921 | |
1186 | |
922 | =item C<EV_FORK> |
1187 | =item C<EV_FORK> |
923 | |
1188 | |
924 | The event loop has been resumed in the child process after fork (see |
1189 | The event loop has been resumed in the child process after fork (see |
925 | C<ev_fork>). |
1190 | C<ev_fork>). |
926 | |
1191 | |
|
|
1192 | =item C<EV_CLEANUP> |
|
|
1193 | |
|
|
1194 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1195 | |
927 | =item C<EV_ASYNC> |
1196 | =item C<EV_ASYNC> |
928 | |
1197 | |
929 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1198 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1199 | |
|
|
1200 | =item C<EV_CUSTOM> |
|
|
1201 | |
|
|
1202 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1203 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
930 | |
1204 | |
931 | =item C<EV_ERROR> |
1205 | =item C<EV_ERROR> |
932 | |
1206 | |
933 | An unspecified error has occurred, the watcher has been stopped. This might |
1207 | An unspecified error has occurred, the watcher has been stopped. This might |
934 | happen because the watcher could not be properly started because libev |
1208 | happen because the watcher could not be properly started because libev |
… | |
… | |
972 | |
1246 | |
973 | ev_io w; |
1247 | ev_io w; |
974 | ev_init (&w, my_cb); |
1248 | ev_init (&w, my_cb); |
975 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1249 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
976 | |
1250 | |
977 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1251 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
978 | |
1252 | |
979 | This macro initialises the type-specific parts of a watcher. You need to |
1253 | This macro initialises the type-specific parts of a watcher. You need to |
980 | call C<ev_init> at least once before you call this macro, but you can |
1254 | call C<ev_init> at least once before you call this macro, but you can |
981 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1255 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
982 | macro on a watcher that is active (it can be pending, however, which is a |
1256 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
995 | |
1269 | |
996 | Example: Initialise and set an C<ev_io> watcher in one step. |
1270 | Example: Initialise and set an C<ev_io> watcher in one step. |
997 | |
1271 | |
998 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1272 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
999 | |
1273 | |
1000 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1274 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1001 | |
1275 | |
1002 | Starts (activates) the given watcher. Only active watchers will receive |
1276 | Starts (activates) the given watcher. Only active watchers will receive |
1003 | events. If the watcher is already active nothing will happen. |
1277 | events. If the watcher is already active nothing will happen. |
1004 | |
1278 | |
1005 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1279 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1006 | whole section. |
1280 | whole section. |
1007 | |
1281 | |
1008 | ev_io_start (EV_DEFAULT_UC, &w); |
1282 | ev_io_start (EV_DEFAULT_UC, &w); |
1009 | |
1283 | |
1010 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1284 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1011 | |
1285 | |
1012 | Stops the given watcher if active, and clears the pending status (whether |
1286 | Stops the given watcher if active, and clears the pending status (whether |
1013 | the watcher was active or not). |
1287 | the watcher was active or not). |
1014 | |
1288 | |
1015 | It is possible that stopped watchers are pending - for example, |
1289 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1040 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1314 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1041 | |
1315 | |
1042 | Change the callback. You can change the callback at virtually any time |
1316 | Change the callback. You can change the callback at virtually any time |
1043 | (modulo threads). |
1317 | (modulo threads). |
1044 | |
1318 | |
1045 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1319 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1046 | |
1320 | |
1047 | =item int ev_priority (ev_TYPE *watcher) |
1321 | =item int ev_priority (ev_TYPE *watcher) |
1048 | |
1322 | |
1049 | Set and query the priority of the watcher. The priority is a small |
1323 | Set and query the priority of the watcher. The priority is a small |
1050 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1324 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1051 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1325 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1052 | before watchers with lower priority, but priority will not keep watchers |
1326 | before watchers with lower priority, but priority will not keep watchers |
1053 | from being executed (except for C<ev_idle> watchers). |
1327 | from being executed (except for C<ev_idle> watchers). |
1054 | |
1328 | |
1055 | This means that priorities are I<only> used for ordering callback |
|
|
1056 | invocation after new events have been received. This is useful, for |
|
|
1057 | example, to reduce latency after idling, or more often, to bind two |
|
|
1058 | watchers on the same event and make sure one is called first. |
|
|
1059 | |
|
|
1060 | If you need to suppress invocation when higher priority events are pending |
1329 | If you need to suppress invocation when higher priority events are pending |
1061 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1330 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1062 | |
1331 | |
1063 | You I<must not> change the priority of a watcher as long as it is active or |
1332 | You I<must not> change the priority of a watcher as long as it is active or |
1064 | pending. |
1333 | pending. |
1065 | |
|
|
1066 | The default priority used by watchers when no priority has been set is |
|
|
1067 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1068 | |
1334 | |
1069 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1335 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1070 | fine, as long as you do not mind that the priority value you query might |
1336 | fine, as long as you do not mind that the priority value you query might |
1071 | or might not have been clamped to the valid range. |
1337 | or might not have been clamped to the valid range. |
|
|
1338 | |
|
|
1339 | The default priority used by watchers when no priority has been set is |
|
|
1340 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1341 | |
|
|
1342 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1343 | priorities. |
1072 | |
1344 | |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1345 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1074 | |
1346 | |
1075 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1347 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1076 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1348 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1084 | watcher isn't pending it does nothing and returns C<0>. |
1356 | watcher isn't pending it does nothing and returns C<0>. |
1085 | |
1357 | |
1086 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1358 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1087 | callback to be invoked, which can be accomplished with this function. |
1359 | callback to be invoked, which can be accomplished with this function. |
1088 | |
1360 | |
|
|
1361 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1362 | |
|
|
1363 | Feeds the given event set into the event loop, as if the specified event |
|
|
1364 | had happened for the specified watcher (which must be a pointer to an |
|
|
1365 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1366 | not free the watcher as long as it has pending events. |
|
|
1367 | |
|
|
1368 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1369 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1370 | not started in the first place. |
|
|
1371 | |
|
|
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1373 | functions that do not need a watcher. |
|
|
1374 | |
1089 | =back |
1375 | =back |
1090 | |
1376 | |
|
|
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1378 | OWN COMPOSITE WATCHERS> idioms. |
1091 | |
1379 | |
1092 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1380 | =head2 WATCHER STATES |
1093 | |
1381 | |
1094 | Each watcher has, by default, a member C<void *data> that you can change |
1382 | There are various watcher states mentioned throughout this manual - |
1095 | and read at any time: libev will completely ignore it. This can be used |
1383 | active, pending and so on. In this section these states and the rules to |
1096 | to associate arbitrary data with your watcher. If you need more data and |
1384 | transition between them will be described in more detail - and while these |
1097 | don't want to allocate memory and store a pointer to it in that data |
1385 | rules might look complicated, they usually do "the right thing". |
1098 | member, you can also "subclass" the watcher type and provide your own |
|
|
1099 | data: |
|
|
1100 | |
1386 | |
1101 | struct my_io |
1387 | =over 4 |
|
|
1388 | |
|
|
1389 | =item initialiased |
|
|
1390 | |
|
|
1391 | Before a watcher can be registered with the event loop it has to be |
|
|
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1394 | |
|
|
1395 | In this state it is simply some block of memory that is suitable for |
|
|
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1397 | will - as long as you either keep the memory contents intact, or call |
|
|
1398 | C<ev_TYPE_init> again. |
|
|
1399 | |
|
|
1400 | =item started/running/active |
|
|
1401 | |
|
|
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1403 | property of the event loop, and is actively waiting for events. While in |
|
|
1404 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1405 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1406 | and call libev functions on it that are documented to work on active watchers. |
|
|
1407 | |
|
|
1408 | =item pending |
|
|
1409 | |
|
|
1410 | If a watcher is active and libev determines that an event it is interested |
|
|
1411 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1412 | stay in this pending state until either it is stopped or its callback is |
|
|
1413 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1414 | callback. |
|
|
1415 | |
|
|
1416 | The watcher might or might not be active while it is pending (for example, |
|
|
1417 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1418 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1419 | but it is still property of the event loop at this time, so cannot be |
|
|
1420 | moved, freed or reused. And if it is active the rules described in the |
|
|
1421 | previous item still apply. |
|
|
1422 | |
|
|
1423 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1424 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1425 | active. |
|
|
1426 | |
|
|
1427 | =item stopped |
|
|
1428 | |
|
|
1429 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1430 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1431 | latter will clear any pending state the watcher might be in, regardless |
|
|
1432 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1433 | freeing it is often a good idea. |
|
|
1434 | |
|
|
1435 | While stopped (and not pending) the watcher is essentially in the |
|
|
1436 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
|
|
1439 | |
|
|
1440 | =back |
|
|
1441 | |
|
|
1442 | =head2 WATCHER PRIORITY MODELS |
|
|
1443 | |
|
|
1444 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1445 | integers that influence the ordering of event callback invocation |
|
|
1446 | between watchers in some way, all else being equal. |
|
|
1447 | |
|
|
1448 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1449 | description for the more technical details such as the actual priority |
|
|
1450 | range. |
|
|
1451 | |
|
|
1452 | There are two common ways how these these priorities are being interpreted |
|
|
1453 | by event loops: |
|
|
1454 | |
|
|
1455 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1456 | of lower priority watchers, which means as long as higher priority |
|
|
1457 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1458 | |
|
|
1459 | The less common only-for-ordering model uses priorities solely to order |
|
|
1460 | callback invocation within a single event loop iteration: Higher priority |
|
|
1461 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1462 | before polling for new events. |
|
|
1463 | |
|
|
1464 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1465 | except for idle watchers (which use the lock-out model). |
|
|
1466 | |
|
|
1467 | The rationale behind this is that implementing the lock-out model for |
|
|
1468 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1469 | libraries will just poll for the same events again and again as long as |
|
|
1470 | their callbacks have not been executed, which is very inefficient in the |
|
|
1471 | common case of one high-priority watcher locking out a mass of lower |
|
|
1472 | priority ones. |
|
|
1473 | |
|
|
1474 | Static (ordering) priorities are most useful when you have two or more |
|
|
1475 | watchers handling the same resource: a typical usage example is having an |
|
|
1476 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1477 | timeouts. Under load, data might be received while the program handles |
|
|
1478 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1479 | handler will be executed before checking for data. In that case, giving |
|
|
1480 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1481 | handled first even under adverse conditions (which is usually, but not |
|
|
1482 | always, what you want). |
|
|
1483 | |
|
|
1484 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1485 | will only be executed when no same or higher priority watchers have |
|
|
1486 | received events, they can be used to implement the "lock-out" model when |
|
|
1487 | required. |
|
|
1488 | |
|
|
1489 | For example, to emulate how many other event libraries handle priorities, |
|
|
1490 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1491 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1492 | processing is done in the idle watcher callback. This causes libev to |
|
|
1493 | continuously poll and process kernel event data for the watcher, but when |
|
|
1494 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1495 | workable. |
|
|
1496 | |
|
|
1497 | Usually, however, the lock-out model implemented that way will perform |
|
|
1498 | miserably under the type of load it was designed to handle. In that case, |
|
|
1499 | it might be preferable to stop the real watcher before starting the |
|
|
1500 | idle watcher, so the kernel will not have to process the event in case |
|
|
1501 | the actual processing will be delayed for considerable time. |
|
|
1502 | |
|
|
1503 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1504 | priority than the default, and which should only process data when no |
|
|
1505 | other events are pending: |
|
|
1506 | |
|
|
1507 | ev_idle idle; // actual processing watcher |
|
|
1508 | ev_io io; // actual event watcher |
|
|
1509 | |
|
|
1510 | static void |
|
|
1511 | io_cb (EV_P_ ev_io *w, int revents) |
1102 | { |
1512 | { |
1103 | ev_io io; |
1513 | // stop the I/O watcher, we received the event, but |
1104 | int otherfd; |
1514 | // are not yet ready to handle it. |
1105 | void *somedata; |
1515 | ev_io_stop (EV_A_ w); |
1106 | struct whatever *mostinteresting; |
1516 | |
|
|
1517 | // start the idle watcher to handle the actual event. |
|
|
1518 | // it will not be executed as long as other watchers |
|
|
1519 | // with the default priority are receiving events. |
|
|
1520 | ev_idle_start (EV_A_ &idle); |
1107 | }; |
1521 | } |
1108 | |
1522 | |
1109 | ... |
1523 | static void |
1110 | struct my_io w; |
1524 | idle_cb (EV_P_ ev_idle *w, int revents) |
1111 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1112 | |
|
|
1113 | And since your callback will be called with a pointer to the watcher, you |
|
|
1114 | can cast it back to your own type: |
|
|
1115 | |
|
|
1116 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1117 | { |
1525 | { |
1118 | struct my_io *w = (struct my_io *)w_; |
1526 | // actual processing |
1119 | ... |
1527 | read (STDIN_FILENO, ...); |
|
|
1528 | |
|
|
1529 | // have to start the I/O watcher again, as |
|
|
1530 | // we have handled the event |
|
|
1531 | ev_io_start (EV_P_ &io); |
1120 | } |
1532 | } |
1121 | |
1533 | |
1122 | More interesting and less C-conformant ways of casting your callback type |
1534 | // initialisation |
1123 | instead have been omitted. |
1535 | ev_idle_init (&idle, idle_cb); |
|
|
1536 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1537 | ev_io_start (EV_DEFAULT_ &io); |
1124 | |
1538 | |
1125 | Another common scenario is to use some data structure with multiple |
1539 | In the "real" world, it might also be beneficial to start a timer, so that |
1126 | embedded watchers: |
1540 | low-priority connections can not be locked out forever under load. This |
1127 | |
1541 | enables your program to keep a lower latency for important connections |
1128 | struct my_biggy |
1542 | during short periods of high load, while not completely locking out less |
1129 | { |
1543 | important ones. |
1130 | int some_data; |
|
|
1131 | ev_timer t1; |
|
|
1132 | ev_timer t2; |
|
|
1133 | } |
|
|
1134 | |
|
|
1135 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1136 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1137 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1138 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1139 | programmers): |
|
|
1140 | |
|
|
1141 | #include <stddef.h> |
|
|
1142 | |
|
|
1143 | static void |
|
|
1144 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1145 | { |
|
|
1146 | struct my_biggy big = (struct my_biggy * |
|
|
1147 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1148 | } |
|
|
1149 | |
|
|
1150 | static void |
|
|
1151 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1152 | { |
|
|
1153 | struct my_biggy big = (struct my_biggy * |
|
|
1154 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1155 | } |
|
|
1156 | |
1544 | |
1157 | |
1545 | |
1158 | =head1 WATCHER TYPES |
1546 | =head1 WATCHER TYPES |
1159 | |
1547 | |
1160 | This section describes each watcher in detail, but will not repeat |
1548 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1184 | In general you can register as many read and/or write event watchers per |
1572 | In general you can register as many read and/or write event watchers per |
1185 | fd as you want (as long as you don't confuse yourself). Setting all file |
1573 | fd as you want (as long as you don't confuse yourself). Setting all file |
1186 | descriptors to non-blocking mode is also usually a good idea (but not |
1574 | descriptors to non-blocking mode is also usually a good idea (but not |
1187 | required if you know what you are doing). |
1575 | required if you know what you are doing). |
1188 | |
1576 | |
1189 | If you cannot use non-blocking mode, then force the use of a |
|
|
1190 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1191 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
|
|
1192 | |
|
|
1193 | Another thing you have to watch out for is that it is quite easy to |
1577 | Another thing you have to watch out for is that it is quite easy to |
1194 | receive "spurious" readiness notifications, that is your callback might |
1578 | receive "spurious" readiness notifications, that is, your callback might |
1195 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1196 | because there is no data. Not only are some backends known to create a |
1580 | because there is no data. It is very easy to get into this situation even |
1197 | lot of those (for example Solaris ports), it is very easy to get into |
1581 | with a relatively standard program structure. Thus it is best to always |
1198 | this situation even with a relatively standard program structure. Thus |
1582 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1199 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1200 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1583 | preferable to a program hanging until some data arrives. |
1201 | |
1584 | |
1202 | If you cannot run the fd in non-blocking mode (for example you should |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1203 | not play around with an Xlib connection), then you have to separately |
1586 | not play around with an Xlib connection), then you have to separately |
1204 | re-test whether a file descriptor is really ready with a known-to-be good |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1205 | interface such as poll (fortunately in our Xlib example, Xlib already |
1588 | interface such as poll (fortunately in the case of Xlib, it already does |
1206 | does this on its own, so its quite safe to use). Some people additionally |
1589 | this on its own, so its quite safe to use). Some people additionally |
1207 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1208 | indefinitely. |
1591 | indefinitely. |
1209 | |
1592 | |
1210 | But really, best use non-blocking mode. |
1593 | But really, best use non-blocking mode. |
1211 | |
1594 | |
… | |
… | |
1239 | |
1622 | |
1240 | There is no workaround possible except not registering events |
1623 | There is no workaround possible except not registering events |
1241 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1242 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1243 | |
1626 | |
|
|
1627 | =head3 The special problem of files |
|
|
1628 | |
|
|
1629 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1630 | representing files, and expect it to become ready when their program |
|
|
1631 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1632 | |
|
|
1633 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1634 | notification as soon as the kernel knows whether and how much data is |
|
|
1635 | there, and in the case of open files, that's always the case, so you |
|
|
1636 | always get a readiness notification instantly, and your read (or possibly |
|
|
1637 | write) will still block on the disk I/O. |
|
|
1638 | |
|
|
1639 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1640 | devices and so on, there is another party (the sender) that delivers data |
|
|
1641 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1642 | will not send data on its own, simply because it doesn't know what you |
|
|
1643 | wish to read - you would first have to request some data. |
|
|
1644 | |
|
|
1645 | Since files are typically not-so-well supported by advanced notification |
|
|
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1647 | to files, even though you should not use it. The reason for this is |
|
|
1648 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1649 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1650 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1651 | F</dev/urandom>), and even though the file might better be served with |
|
|
1652 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1653 | it "just works" instead of freezing. |
|
|
1654 | |
|
|
1655 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1656 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1657 | when you rarely read from a file instead of from a socket, and want to |
|
|
1658 | reuse the same code path. |
|
|
1659 | |
1244 | =head3 The special problem of fork |
1660 | =head3 The special problem of fork |
1245 | |
1661 | |
1246 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1662 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1247 | useless behaviour. Libev fully supports fork, but needs to be told about |
1663 | useless behaviour. Libev fully supports fork, but needs to be told about |
1248 | it in the child. |
1664 | it in the child if you want to continue to use it in the child. |
1249 | |
1665 | |
1250 | To support fork in your programs, you either have to call |
1666 | To support fork in your child processes, you have to call C<ev_loop_fork |
1251 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1667 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1252 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1253 | C<EVBACKEND_POLL>. |
|
|
1254 | |
1669 | |
1255 | =head3 The special problem of SIGPIPE |
1670 | =head3 The special problem of SIGPIPE |
1256 | |
1671 | |
1257 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1672 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1258 | when writing to a pipe whose other end has been closed, your program gets |
1673 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1261 | |
1676 | |
1262 | So when you encounter spurious, unexplained daemon exits, make sure you |
1677 | So when you encounter spurious, unexplained daemon exits, make sure you |
1263 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1678 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1264 | somewhere, as that would have given you a big clue). |
1679 | somewhere, as that would have given you a big clue). |
1265 | |
1680 | |
|
|
1681 | =head3 The special problem of accept()ing when you can't |
|
|
1682 | |
|
|
1683 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1684 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1685 | connection from the pending queue in all error cases. |
|
|
1686 | |
|
|
1687 | For example, larger servers often run out of file descriptors (because |
|
|
1688 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1689 | rejecting the connection, leading to libev signalling readiness on |
|
|
1690 | the next iteration again (the connection still exists after all), and |
|
|
1691 | typically causing the program to loop at 100% CPU usage. |
|
|
1692 | |
|
|
1693 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1694 | operating systems, there is usually little the app can do to remedy the |
|
|
1695 | situation, and no known thread-safe method of removing the connection to |
|
|
1696 | cope with overload is known (to me). |
|
|
1697 | |
|
|
1698 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1699 | - when the program encounters an overload, it will just loop until the |
|
|
1700 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1701 | event-based way to handle this situation, so it's the best one can do. |
|
|
1702 | |
|
|
1703 | A better way to handle the situation is to log any errors other than |
|
|
1704 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1705 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1706 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1707 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1708 | usage. |
|
|
1709 | |
|
|
1710 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1711 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1712 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1713 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1714 | clients under typical overload conditions. |
|
|
1715 | |
|
|
1716 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1717 | is often done with C<malloc> failures, but this results in an easy |
|
|
1718 | opportunity for a DoS attack. |
1266 | |
1719 | |
1267 | =head3 Watcher-Specific Functions |
1720 | =head3 Watcher-Specific Functions |
1268 | |
1721 | |
1269 | =over 4 |
1722 | =over 4 |
1270 | |
1723 | |
… | |
… | |
1302 | ... |
1755 | ... |
1303 | struct ev_loop *loop = ev_default_init (0); |
1756 | struct ev_loop *loop = ev_default_init (0); |
1304 | ev_io stdin_readable; |
1757 | ev_io stdin_readable; |
1305 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1758 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1306 | ev_io_start (loop, &stdin_readable); |
1759 | ev_io_start (loop, &stdin_readable); |
1307 | ev_loop (loop, 0); |
1760 | ev_run (loop, 0); |
1308 | |
1761 | |
1309 | |
1762 | |
1310 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1763 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1311 | |
1764 | |
1312 | Timer watchers are simple relative timers that generate an event after a |
1765 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1317 | year, it will still time out after (roughly) one hour. "Roughly" because |
1770 | year, it will still time out after (roughly) one hour. "Roughly" because |
1318 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
1320 | |
1773 | |
1321 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1322 | passed, but if multiple timers become ready during the same loop iteration |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1323 | then order of execution is undefined. |
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
|
|
1778 | iteration then the ones with earlier time-out values are invoked before |
|
|
1779 | ones of the same priority with later time-out values (but this is no |
|
|
1780 | longer true when a callback calls C<ev_run> recursively). |
1324 | |
1781 | |
1325 | =head3 Be smart about timeouts |
1782 | =head3 Be smart about timeouts |
1326 | |
1783 | |
1327 | Many real-world problems involve some kind of timeout, usually for error |
1784 | Many real-world problems involve some kind of timeout, usually for error |
1328 | recovery. A typical example is an HTTP request - if the other side hangs, |
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1372 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1829 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1373 | member and C<ev_timer_again>. |
1830 | member and C<ev_timer_again>. |
1374 | |
1831 | |
1375 | At start: |
1832 | At start: |
1376 | |
1833 | |
1377 | ev_timer_init (timer, callback); |
1834 | ev_init (timer, callback); |
1378 | timer->repeat = 60.; |
1835 | timer->repeat = 60.; |
1379 | ev_timer_again (loop, timer); |
1836 | ev_timer_again (loop, timer); |
1380 | |
1837 | |
1381 | Each time there is some activity: |
1838 | Each time there is some activity: |
1382 | |
1839 | |
… | |
… | |
1414 | ev_tstamp timeout = last_activity + 60.; |
1871 | ev_tstamp timeout = last_activity + 60.; |
1415 | |
1872 | |
1416 | // if last_activity + 60. is older than now, we did time out |
1873 | // if last_activity + 60. is older than now, we did time out |
1417 | if (timeout < now) |
1874 | if (timeout < now) |
1418 | { |
1875 | { |
1419 | // timeout occured, take action |
1876 | // timeout occurred, take action |
1420 | } |
1877 | } |
1421 | else |
1878 | else |
1422 | { |
1879 | { |
1423 | // callback was invoked, but there was some activity, re-arm |
1880 | // callback was invoked, but there was some activity, re-arm |
1424 | // the watcher to fire in last_activity + 60, which is |
1881 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1444 | |
1901 | |
1445 | To start the timer, simply initialise the watcher and set C<last_activity> |
1902 | To start the timer, simply initialise the watcher and set C<last_activity> |
1446 | to the current time (meaning we just have some activity :), then call the |
1903 | to the current time (meaning we just have some activity :), then call the |
1447 | callback, which will "do the right thing" and start the timer: |
1904 | callback, which will "do the right thing" and start the timer: |
1448 | |
1905 | |
1449 | ev_timer_init (timer, callback); |
1906 | ev_init (timer, callback); |
1450 | last_activity = ev_now (loop); |
1907 | last_activity = ev_now (loop); |
1451 | callback (loop, timer, EV_TIMEOUT); |
1908 | callback (loop, timer, EV_TIMER); |
1452 | |
1909 | |
1453 | And when there is some activity, simply store the current time in |
1910 | And when there is some activity, simply store the current time in |
1454 | C<last_activity>, no libev calls at all: |
1911 | C<last_activity>, no libev calls at all: |
1455 | |
1912 | |
1456 | last_actiivty = ev_now (loop); |
1913 | last_activity = ev_now (loop); |
1457 | |
1914 | |
1458 | This technique is slightly more complex, but in most cases where the |
1915 | This technique is slightly more complex, but in most cases where the |
1459 | time-out is unlikely to be triggered, much more efficient. |
1916 | time-out is unlikely to be triggered, much more efficient. |
1460 | |
1917 | |
1461 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1918 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1495 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1952 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1496 | rather complicated, but extremely efficient, something that really pays |
1953 | rather complicated, but extremely efficient, something that really pays |
1497 | off after the first million or so of active timers, i.e. it's usually |
1954 | off after the first million or so of active timers, i.e. it's usually |
1498 | overkill :) |
1955 | overkill :) |
1499 | |
1956 | |
|
|
1957 | =head3 The special problem of being too early |
|
|
1958 | |
|
|
1959 | If you ask a timer to call your callback after three seconds, then |
|
|
1960 | you expect it to be invoked after three seconds - but of course, this |
|
|
1961 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1962 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1963 | process a STOP signal for a few hours for example. |
|
|
1964 | |
|
|
1965 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1966 | delay has occurred, but cannot guarantee this. |
|
|
1967 | |
|
|
1968 | A less obvious failure mode is calling your callback too early: many event |
|
|
1969 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1970 | this can cause your callback to be invoked much earlier than you would |
|
|
1971 | expect. |
|
|
1972 | |
|
|
1973 | To see why, imagine a system with a clock that only offers full second |
|
|
1974 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1975 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1976 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1977 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1978 | |
|
|
1979 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1980 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1981 | one-second delay was requested - this is being "too early", despite best |
|
|
1982 | intentions. |
|
|
1983 | |
|
|
1984 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1985 | delay equals the requested delay, but only when the elapsed delay is |
|
|
1986 | larger than the requested delay. In the example above, libev would only invoke |
|
|
1987 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
1988 | |
|
|
1989 | So, while libev cannot guarantee that your callback will be invoked |
|
|
1990 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
1991 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
1992 | late" side of things. |
|
|
1993 | |
1500 | =head3 The special problem of time updates |
1994 | =head3 The special problem of time updates |
1501 | |
1995 | |
1502 | Establishing the current time is a costly operation (it usually takes at |
1996 | Establishing the current time is a costly operation (it usually takes |
1503 | least two system calls): EV therefore updates its idea of the current |
1997 | at least one system call): EV therefore updates its idea of the current |
1504 | time only before and after C<ev_loop> collects new events, which causes a |
1998 | time only before and after C<ev_run> collects new events, which causes a |
1505 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1999 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1506 | lots of events in one iteration. |
2000 | lots of events in one iteration. |
1507 | |
2001 | |
1508 | The relative timeouts are calculated relative to the C<ev_now ()> |
2002 | The relative timeouts are calculated relative to the C<ev_now ()> |
1509 | time. This is usually the right thing as this timestamp refers to the time |
2003 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1515 | |
2009 | |
1516 | If the event loop is suspended for a long time, you can also force an |
2010 | If the event loop is suspended for a long time, you can also force an |
1517 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2011 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1518 | ()>. |
2012 | ()>. |
1519 | |
2013 | |
|
|
2014 | =head3 The special problem of unsynchronised clocks |
|
|
2015 | |
|
|
2016 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2017 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2018 | jumps). |
|
|
2019 | |
|
|
2020 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2021 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2022 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2023 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2024 | than a directly following call to C<time>. |
|
|
2025 | |
|
|
2026 | The moral of this is to only compare libev-related timestamps with |
|
|
2027 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2028 | a second or so. |
|
|
2029 | |
|
|
2030 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2031 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2032 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2033 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2034 | |
|
|
2035 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2036 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2037 | I<measured according to the real time>, not the system clock. |
|
|
2038 | |
|
|
2039 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2040 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2041 | exactly the right behaviour. |
|
|
2042 | |
|
|
2043 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2044 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2045 | time, where your comparisons will always generate correct results. |
|
|
2046 | |
|
|
2047 | =head3 The special problems of suspended animation |
|
|
2048 | |
|
|
2049 | When you leave the server world it is quite customary to hit machines that |
|
|
2050 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2051 | |
|
|
2052 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2053 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2054 | to run until the system is suspended, but they will not advance while the |
|
|
2055 | system is suspended. That means, on resume, it will be as if the program |
|
|
2056 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2057 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2058 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2059 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2060 | be adjusted accordingly. |
|
|
2061 | |
|
|
2062 | I would not be surprised to see different behaviour in different between |
|
|
2063 | operating systems, OS versions or even different hardware. |
|
|
2064 | |
|
|
2065 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2066 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2067 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2068 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2069 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2070 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2071 | |
|
|
2072 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2073 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2074 | deterministic behaviour in this case (you can do nothing against |
|
|
2075 | C<SIGSTOP>). |
|
|
2076 | |
1520 | =head3 Watcher-Specific Functions and Data Members |
2077 | =head3 Watcher-Specific Functions and Data Members |
1521 | |
2078 | |
1522 | =over 4 |
2079 | =over 4 |
1523 | |
2080 | |
1524 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2081 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1537 | keep up with the timer (because it takes longer than those 10 seconds to |
2094 | keep up with the timer (because it takes longer than those 10 seconds to |
1538 | do stuff) the timer will not fire more than once per event loop iteration. |
2095 | do stuff) the timer will not fire more than once per event loop iteration. |
1539 | |
2096 | |
1540 | =item ev_timer_again (loop, ev_timer *) |
2097 | =item ev_timer_again (loop, ev_timer *) |
1541 | |
2098 | |
1542 | This will act as if the timer timed out and restart it again if it is |
2099 | This will act as if the timer timed out and restarts it again if it is |
1543 | repeating. The exact semantics are: |
2100 | repeating. The exact semantics are: |
1544 | |
2101 | |
1545 | If the timer is pending, its pending status is cleared. |
2102 | If the timer is pending, its pending status is cleared. |
1546 | |
2103 | |
1547 | If the timer is started but non-repeating, stop it (as if it timed out). |
2104 | If the timer is started but non-repeating, stop it (as if it timed out). |
1548 | |
2105 | |
1549 | If the timer is repeating, either start it if necessary (with the |
2106 | If the timer is repeating, either start it if necessary (with the |
1550 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2107 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1551 | |
2108 | |
1552 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
2109 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1553 | usage example. |
2110 | usage example. |
|
|
2111 | |
|
|
2112 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
2113 | |
|
|
2114 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
2115 | then this time is relative to the current event loop time, otherwise it's |
|
|
2116 | the timeout value currently configured. |
|
|
2117 | |
|
|
2118 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2119 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2120 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2121 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2122 | too), and so on. |
1554 | |
2123 | |
1555 | =item ev_tstamp repeat [read-write] |
2124 | =item ev_tstamp repeat [read-write] |
1556 | |
2125 | |
1557 | The current C<repeat> value. Will be used each time the watcher times out |
2126 | The current C<repeat> value. Will be used each time the watcher times out |
1558 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2127 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1584 | } |
2153 | } |
1585 | |
2154 | |
1586 | ev_timer mytimer; |
2155 | ev_timer mytimer; |
1587 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2156 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1588 | ev_timer_again (&mytimer); /* start timer */ |
2157 | ev_timer_again (&mytimer); /* start timer */ |
1589 | ev_loop (loop, 0); |
2158 | ev_run (loop, 0); |
1590 | |
2159 | |
1591 | // and in some piece of code that gets executed on any "activity": |
2160 | // and in some piece of code that gets executed on any "activity": |
1592 | // reset the timeout to start ticking again at 10 seconds |
2161 | // reset the timeout to start ticking again at 10 seconds |
1593 | ev_timer_again (&mytimer); |
2162 | ev_timer_again (&mytimer); |
1594 | |
2163 | |
… | |
… | |
1617 | timers, such as triggering an event on each "midnight, local time", or |
2186 | timers, such as triggering an event on each "midnight, local time", or |
1618 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2187 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1619 | those cannot react to time jumps. |
2188 | those cannot react to time jumps. |
1620 | |
2189 | |
1621 | As with timers, the callback is guaranteed to be invoked only when the |
2190 | As with timers, the callback is guaranteed to be invoked only when the |
1622 | point in time where it is supposed to trigger has passed, but if multiple |
2191 | point in time where it is supposed to trigger has passed. If multiple |
1623 | periodic timers become ready during the same loop iteration, then order of |
2192 | timers become ready during the same loop iteration then the ones with |
1624 | execution is undefined. |
2193 | earlier time-out values are invoked before ones with later time-out values |
|
|
2194 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1625 | |
2195 | |
1626 | =head3 Watcher-Specific Functions and Data Members |
2196 | =head3 Watcher-Specific Functions and Data Members |
1627 | |
2197 | |
1628 | =over 4 |
2198 | =over 4 |
1629 | |
2199 | |
… | |
… | |
1664 | |
2234 | |
1665 | Another way to think about it (for the mathematically inclined) is that |
2235 | Another way to think about it (for the mathematically inclined) is that |
1666 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2236 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1667 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2237 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1668 | |
2238 | |
1669 | For numerical stability it is preferable that the C<offset> value is near |
2239 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1670 | C<ev_now ()> (the current time), but there is no range requirement for |
2240 | interval value should be higher than C<1/8192> (which is around 100 |
1671 | this value, and in fact is often specified as zero. |
2241 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2242 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2243 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2244 | C<0> and C<interval>, which is also the recommended range. |
1672 | |
2245 | |
1673 | Note also that there is an upper limit to how often a timer can fire (CPU |
2246 | Note also that there is an upper limit to how often a timer can fire (CPU |
1674 | speed for example), so if C<interval> is very small then timing stability |
2247 | speed for example), so if C<interval> is very small then timing stability |
1675 | will of course deteriorate. Libev itself tries to be exact to be about one |
2248 | will of course deteriorate. Libev itself tries to be exact to be about one |
1676 | millisecond (if the OS supports it and the machine is fast enough). |
2249 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
1757 | Example: Call a callback every hour, or, more precisely, whenever the |
2330 | Example: Call a callback every hour, or, more precisely, whenever the |
1758 | system time is divisible by 3600. The callback invocation times have |
2331 | system time is divisible by 3600. The callback invocation times have |
1759 | potentially a lot of jitter, but good long-term stability. |
2332 | potentially a lot of jitter, but good long-term stability. |
1760 | |
2333 | |
1761 | static void |
2334 | static void |
1762 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2335 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1763 | { |
2336 | { |
1764 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2337 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1765 | } |
2338 | } |
1766 | |
2339 | |
1767 | ev_periodic hourly_tick; |
2340 | ev_periodic hourly_tick; |
… | |
… | |
1790 | |
2363 | |
1791 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2364 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1792 | |
2365 | |
1793 | Signal watchers will trigger an event when the process receives a specific |
2366 | Signal watchers will trigger an event when the process receives a specific |
1794 | signal one or more times. Even though signals are very asynchronous, libev |
2367 | signal one or more times. Even though signals are very asynchronous, libev |
1795 | will try it's best to deliver signals synchronously, i.e. as part of the |
2368 | will try its best to deliver signals synchronously, i.e. as part of the |
1796 | normal event processing, like any other event. |
2369 | normal event processing, like any other event. |
1797 | |
2370 | |
1798 | If you want signals asynchronously, just use C<sigaction> as you would |
2371 | If you want signals to be delivered truly asynchronously, just use |
1799 | do without libev and forget about sharing the signal. You can even use |
2372 | C<sigaction> as you would do without libev and forget about sharing |
1800 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2373 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2374 | synchronously wake up an event loop. |
1801 | |
2375 | |
1802 | You can configure as many watchers as you like per signal. Only when the |
2376 | You can configure as many watchers as you like for the same signal, but |
|
|
2377 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2378 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2379 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2380 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2381 | |
1803 | first watcher gets started will libev actually register a signal handler |
2382 | When the first watcher gets started will libev actually register something |
1804 | with the kernel (thus it coexists with your own signal handlers as long as |
2383 | with the kernel (thus it coexists with your own signal handlers as long as |
1805 | you don't register any with libev for the same signal). Similarly, when |
2384 | you don't register any with libev for the same signal). |
1806 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1807 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1808 | |
2385 | |
1809 | If possible and supported, libev will install its handlers with |
2386 | If possible and supported, libev will install its handlers with |
1810 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2387 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1811 | interrupted. If you have a problem with system calls getting interrupted by |
2388 | not be unduly interrupted. If you have a problem with system calls getting |
1812 | signals you can block all signals in an C<ev_check> watcher and unblock |
2389 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1813 | them in an C<ev_prepare> watcher. |
2390 | and unblock them in an C<ev_prepare> watcher. |
|
|
2391 | |
|
|
2392 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2393 | |
|
|
2394 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2395 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2396 | stopping it again), that is, libev might or might not block the signal, |
|
|
2397 | and might or might not set or restore the installed signal handler (but |
|
|
2398 | see C<EVFLAG_NOSIGMASK>). |
|
|
2399 | |
|
|
2400 | While this does not matter for the signal disposition (libev never |
|
|
2401 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2402 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2403 | certain signals to be blocked. |
|
|
2404 | |
|
|
2405 | This means that before calling C<exec> (from the child) you should reset |
|
|
2406 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2407 | choice usually). |
|
|
2408 | |
|
|
2409 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2410 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2411 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2412 | |
|
|
2413 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2414 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2415 | the window of opportunity for problems, it will not go away, as libev |
|
|
2416 | I<has> to modify the signal mask, at least temporarily. |
|
|
2417 | |
|
|
2418 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2419 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2420 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2421 | |
|
|
2422 | =head3 The special problem of threads signal handling |
|
|
2423 | |
|
|
2424 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2425 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2426 | threads in a process block signals, which is hard to achieve. |
|
|
2427 | |
|
|
2428 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2429 | for the same signals), you can tackle this problem by globally blocking |
|
|
2430 | all signals before creating any threads (or creating them with a fully set |
|
|
2431 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2432 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2433 | these signals. You can pass on any signals that libev might be interested |
|
|
2434 | in by calling C<ev_feed_signal>. |
1814 | |
2435 | |
1815 | =head3 Watcher-Specific Functions and Data Members |
2436 | =head3 Watcher-Specific Functions and Data Members |
1816 | |
2437 | |
1817 | =over 4 |
2438 | =over 4 |
1818 | |
2439 | |
… | |
… | |
1834 | Example: Try to exit cleanly on SIGINT. |
2455 | Example: Try to exit cleanly on SIGINT. |
1835 | |
2456 | |
1836 | static void |
2457 | static void |
1837 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2458 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1838 | { |
2459 | { |
1839 | ev_unloop (loop, EVUNLOOP_ALL); |
2460 | ev_break (loop, EVBREAK_ALL); |
1840 | } |
2461 | } |
1841 | |
2462 | |
1842 | ev_signal signal_watcher; |
2463 | ev_signal signal_watcher; |
1843 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2464 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1844 | ev_signal_start (loop, &signal_watcher); |
2465 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
1850 | some child status changes (most typically when a child of yours dies or |
2471 | some child status changes (most typically when a child of yours dies or |
1851 | exits). It is permissible to install a child watcher I<after> the child |
2472 | exits). It is permissible to install a child watcher I<after> the child |
1852 | has been forked (which implies it might have already exited), as long |
2473 | has been forked (which implies it might have already exited), as long |
1853 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2474 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1854 | forking and then immediately registering a watcher for the child is fine, |
2475 | forking and then immediately registering a watcher for the child is fine, |
1855 | but forking and registering a watcher a few event loop iterations later is |
2476 | but forking and registering a watcher a few event loop iterations later or |
1856 | not. |
2477 | in the next callback invocation is not. |
1857 | |
2478 | |
1858 | Only the default event loop is capable of handling signals, and therefore |
2479 | Only the default event loop is capable of handling signals, and therefore |
1859 | you can only register child watchers in the default event loop. |
2480 | you can only register child watchers in the default event loop. |
1860 | |
2481 | |
|
|
2482 | Due to some design glitches inside libev, child watchers will always be |
|
|
2483 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2484 | libev) |
|
|
2485 | |
1861 | =head3 Process Interaction |
2486 | =head3 Process Interaction |
1862 | |
2487 | |
1863 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2488 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1864 | initialised. This is necessary to guarantee proper behaviour even if |
2489 | initialised. This is necessary to guarantee proper behaviour even if the |
1865 | the first child watcher is started after the child exits. The occurrence |
2490 | first child watcher is started after the child exits. The occurrence |
1866 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2491 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1867 | synchronously as part of the event loop processing. Libev always reaps all |
2492 | synchronously as part of the event loop processing. Libev always reaps all |
1868 | children, even ones not watched. |
2493 | children, even ones not watched. |
1869 | |
2494 | |
1870 | =head3 Overriding the Built-In Processing |
2495 | =head3 Overriding the Built-In Processing |
… | |
… | |
1880 | =head3 Stopping the Child Watcher |
2505 | =head3 Stopping the Child Watcher |
1881 | |
2506 | |
1882 | Currently, the child watcher never gets stopped, even when the |
2507 | Currently, the child watcher never gets stopped, even when the |
1883 | child terminates, so normally one needs to stop the watcher in the |
2508 | child terminates, so normally one needs to stop the watcher in the |
1884 | callback. Future versions of libev might stop the watcher automatically |
2509 | callback. Future versions of libev might stop the watcher automatically |
1885 | when a child exit is detected. |
2510 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2511 | problem). |
1886 | |
2512 | |
1887 | =head3 Watcher-Specific Functions and Data Members |
2513 | =head3 Watcher-Specific Functions and Data Members |
1888 | |
2514 | |
1889 | =over 4 |
2515 | =over 4 |
1890 | |
2516 | |
… | |
… | |
2216 | // no longer anything immediate to do. |
2842 | // no longer anything immediate to do. |
2217 | } |
2843 | } |
2218 | |
2844 | |
2219 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2845 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2220 | ev_idle_init (idle_watcher, idle_cb); |
2846 | ev_idle_init (idle_watcher, idle_cb); |
2221 | ev_idle_start (loop, idle_cb); |
2847 | ev_idle_start (loop, idle_watcher); |
2222 | |
2848 | |
2223 | |
2849 | |
2224 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2850 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2225 | |
2851 | |
2226 | Prepare and check watchers are usually (but not always) used in pairs: |
2852 | Prepare and check watchers are usually (but not always) used in pairs: |
2227 | prepare watchers get invoked before the process blocks and check watchers |
2853 | prepare watchers get invoked before the process blocks and check watchers |
2228 | afterwards. |
2854 | afterwards. |
2229 | |
2855 | |
2230 | You I<must not> call C<ev_loop> or similar functions that enter |
2856 | You I<must not> call C<ev_run> or similar functions that enter |
2231 | the current event loop from either C<ev_prepare> or C<ev_check> |
2857 | the current event loop from either C<ev_prepare> or C<ev_check> |
2232 | watchers. Other loops than the current one are fine, however. The |
2858 | watchers. Other loops than the current one are fine, however. The |
2233 | rationale behind this is that you do not need to check for recursion in |
2859 | rationale behind this is that you do not need to check for recursion in |
2234 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2860 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2235 | C<ev_check> so if you have one watcher of each kind they will always be |
2861 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2319 | struct pollfd fds [nfd]; |
2945 | struct pollfd fds [nfd]; |
2320 | // actual code will need to loop here and realloc etc. |
2946 | // actual code will need to loop here and realloc etc. |
2321 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2947 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2322 | |
2948 | |
2323 | /* the callback is illegal, but won't be called as we stop during check */ |
2949 | /* the callback is illegal, but won't be called as we stop during check */ |
2324 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2950 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2325 | ev_timer_start (loop, &tw); |
2951 | ev_timer_start (loop, &tw); |
2326 | |
2952 | |
2327 | // create one ev_io per pollfd |
2953 | // create one ev_io per pollfd |
2328 | for (int i = 0; i < nfd; ++i) |
2954 | for (int i = 0; i < nfd; ++i) |
2329 | { |
2955 | { |
… | |
… | |
2403 | |
3029 | |
2404 | if (timeout >= 0) |
3030 | if (timeout >= 0) |
2405 | // create/start timer |
3031 | // create/start timer |
2406 | |
3032 | |
2407 | // poll |
3033 | // poll |
2408 | ev_loop (EV_A_ 0); |
3034 | ev_run (EV_A_ 0); |
2409 | |
3035 | |
2410 | // stop timer again |
3036 | // stop timer again |
2411 | if (timeout >= 0) |
3037 | if (timeout >= 0) |
2412 | ev_timer_stop (EV_A_ &to); |
3038 | ev_timer_stop (EV_A_ &to); |
2413 | |
3039 | |
… | |
… | |
2491 | if you do not want that, you need to temporarily stop the embed watcher). |
3117 | if you do not want that, you need to temporarily stop the embed watcher). |
2492 | |
3118 | |
2493 | =item ev_embed_sweep (loop, ev_embed *) |
3119 | =item ev_embed_sweep (loop, ev_embed *) |
2494 | |
3120 | |
2495 | Make a single, non-blocking sweep over the embedded loop. This works |
3121 | Make a single, non-blocking sweep over the embedded loop. This works |
2496 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3122 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2497 | appropriate way for embedded loops. |
3123 | appropriate way for embedded loops. |
2498 | |
3124 | |
2499 | =item struct ev_loop *other [read-only] |
3125 | =item struct ev_loop *other [read-only] |
2500 | |
3126 | |
2501 | The embedded event loop. |
3127 | The embedded event loop. |
… | |
… | |
2559 | event loop blocks next and before C<ev_check> watchers are being called, |
3185 | event loop blocks next and before C<ev_check> watchers are being called, |
2560 | and only in the child after the fork. If whoever good citizen calling |
3186 | and only in the child after the fork. If whoever good citizen calling |
2561 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3187 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2562 | handlers will be invoked, too, of course. |
3188 | handlers will be invoked, too, of course. |
2563 | |
3189 | |
|
|
3190 | =head3 The special problem of life after fork - how is it possible? |
|
|
3191 | |
|
|
3192 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3193 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3194 | sequence should be handled by libev without any problems. |
|
|
3195 | |
|
|
3196 | This changes when the application actually wants to do event handling |
|
|
3197 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3198 | fork. |
|
|
3199 | |
|
|
3200 | The default mode of operation (for libev, with application help to detect |
|
|
3201 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3202 | when I<either> the parent I<or> the child process continues. |
|
|
3203 | |
|
|
3204 | When both processes want to continue using libev, then this is usually the |
|
|
3205 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3206 | supposed to continue with all watchers in place as before, while the other |
|
|
3207 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3208 | |
|
|
3209 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3210 | simply create a new event loop, which of course will be "empty", and |
|
|
3211 | use that for new watchers. This has the advantage of not touching more |
|
|
3212 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3213 | disadvantage of having to use multiple event loops (which do not support |
|
|
3214 | signal watchers). |
|
|
3215 | |
|
|
3216 | When this is not possible, or you want to use the default loop for |
|
|
3217 | other reasons, then in the process that wants to start "fresh", call |
|
|
3218 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3219 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3220 | watchers, so you have to be careful not to execute code that modifies |
|
|
3221 | those watchers. Note also that in that case, you have to re-register any |
|
|
3222 | signal watchers. |
|
|
3223 | |
2564 | =head3 Watcher-Specific Functions and Data Members |
3224 | =head3 Watcher-Specific Functions and Data Members |
2565 | |
3225 | |
2566 | =over 4 |
3226 | =over 4 |
2567 | |
3227 | |
2568 | =item ev_fork_init (ev_signal *, callback) |
3228 | =item ev_fork_init (ev_fork *, callback) |
2569 | |
3229 | |
2570 | Initialises and configures the fork watcher - it has no parameters of any |
3230 | Initialises and configures the fork watcher - it has no parameters of any |
2571 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3231 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2572 | believe me. |
3232 | really. |
2573 | |
3233 | |
2574 | =back |
3234 | =back |
2575 | |
3235 | |
2576 | |
3236 | |
|
|
3237 | =head2 C<ev_cleanup> - even the best things end |
|
|
3238 | |
|
|
3239 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3240 | by a call to C<ev_loop_destroy>. |
|
|
3241 | |
|
|
3242 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3243 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3244 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3245 | loop when you want them to be invoked. |
|
|
3246 | |
|
|
3247 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3248 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3249 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3250 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3251 | |
|
|
3252 | =head3 Watcher-Specific Functions and Data Members |
|
|
3253 | |
|
|
3254 | =over 4 |
|
|
3255 | |
|
|
3256 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3257 | |
|
|
3258 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3259 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3260 | pointless, I assure you. |
|
|
3261 | |
|
|
3262 | =back |
|
|
3263 | |
|
|
3264 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3265 | cleanup functions are called. |
|
|
3266 | |
|
|
3267 | static void |
|
|
3268 | program_exits (void) |
|
|
3269 | { |
|
|
3270 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3271 | } |
|
|
3272 | |
|
|
3273 | ... |
|
|
3274 | atexit (program_exits); |
|
|
3275 | |
|
|
3276 | |
2577 | =head2 C<ev_async> - how to wake up another event loop |
3277 | =head2 C<ev_async> - how to wake up an event loop |
2578 | |
3278 | |
2579 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3279 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2580 | asynchronous sources such as signal handlers (as opposed to multiple event |
3280 | asynchronous sources such as signal handlers (as opposed to multiple event |
2581 | loops - those are of course safe to use in different threads). |
3281 | loops - those are of course safe to use in different threads). |
2582 | |
3282 | |
2583 | Sometimes, however, you need to wake up another event loop you do not |
3283 | Sometimes, however, you need to wake up an event loop you do not control, |
2584 | control, for example because it belongs to another thread. This is what |
3284 | for example because it belongs to another thread. This is what C<ev_async> |
2585 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3285 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2586 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3286 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2587 | safe. |
|
|
2588 | |
3287 | |
2589 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3288 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2590 | too, are asynchronous in nature, and signals, too, will be compressed |
3289 | too, are asynchronous in nature, and signals, too, will be compressed |
2591 | (i.e. the number of callback invocations may be less than the number of |
3290 | (i.e. the number of callback invocations may be less than the number of |
2592 | C<ev_async_sent> calls). |
3291 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
2593 | |
3292 | of "global async watchers" by using a watcher on an otherwise unused |
2594 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3293 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2595 | just the default loop. |
3294 | even without knowing which loop owns the signal. |
2596 | |
3295 | |
2597 | =head3 Queueing |
3296 | =head3 Queueing |
2598 | |
3297 | |
2599 | C<ev_async> does not support queueing of data in any way. The reason |
3298 | C<ev_async> does not support queueing of data in any way. The reason |
2600 | is that the author does not know of a simple (or any) algorithm for a |
3299 | is that the author does not know of a simple (or any) algorithm for a |
2601 | multiple-writer-single-reader queue that works in all cases and doesn't |
3300 | multiple-writer-single-reader queue that works in all cases and doesn't |
2602 | need elaborate support such as pthreads. |
3301 | need elaborate support such as pthreads or unportable memory access |
|
|
3302 | semantics. |
2603 | |
3303 | |
2604 | That means that if you want to queue data, you have to provide your own |
3304 | That means that if you want to queue data, you have to provide your own |
2605 | queue. But at least I can tell you how to implement locking around your |
3305 | queue. But at least I can tell you how to implement locking around your |
2606 | queue: |
3306 | queue: |
2607 | |
3307 | |
… | |
… | |
2691 | trust me. |
3391 | trust me. |
2692 | |
3392 | |
2693 | =item ev_async_send (loop, ev_async *) |
3393 | =item ev_async_send (loop, ev_async *) |
2694 | |
3394 | |
2695 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3395 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2696 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3396 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3397 | returns. |
|
|
3398 | |
2697 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3399 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2698 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3400 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2699 | section below on what exactly this means). |
3401 | embedding section below on what exactly this means). |
2700 | |
3402 | |
2701 | Note that, as with other watchers in libev, multiple events might get |
3403 | Note that, as with other watchers in libev, multiple events might get |
2702 | compressed into a single callback invocation (another way to look at this |
3404 | compressed into a single callback invocation (another way to look at |
2703 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3405 | this is that C<ev_async> watchers are level-triggered: they are set on |
2704 | reset when the event loop detects that). |
3406 | C<ev_async_send>, reset when the event loop detects that). |
2705 | |
3407 | |
2706 | This call incurs the overhead of a system call only once per event loop |
3408 | This call incurs the overhead of at most one extra system call per event |
2707 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3409 | loop iteration, if the event loop is blocked, and no syscall at all if |
2708 | repeated calls to C<ev_async_send> for the same event loop. |
3410 | the event loop (or your program) is processing events. That means that |
|
|
3411 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3412 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3413 | zero) under load. |
2709 | |
3414 | |
2710 | =item bool = ev_async_pending (ev_async *) |
3415 | =item bool = ev_async_pending (ev_async *) |
2711 | |
3416 | |
2712 | Returns a non-zero value when C<ev_async_send> has been called on the |
3417 | Returns a non-zero value when C<ev_async_send> has been called on the |
2713 | watcher but the event has not yet been processed (or even noted) by the |
3418 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2746 | |
3451 | |
2747 | If C<timeout> is less than 0, then no timeout watcher will be |
3452 | If C<timeout> is less than 0, then no timeout watcher will be |
2748 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3453 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2749 | repeat = 0) will be started. C<0> is a valid timeout. |
3454 | repeat = 0) will be started. C<0> is a valid timeout. |
2750 | |
3455 | |
2751 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3456 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2752 | passed an C<revents> set like normal event callbacks (a combination of |
3457 | passed an C<revents> set like normal event callbacks (a combination of |
2753 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3458 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2754 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3459 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2755 | a timeout and an io event at the same time - you probably should give io |
3460 | a timeout and an io event at the same time - you probably should give io |
2756 | events precedence. |
3461 | events precedence. |
2757 | |
3462 | |
2758 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3463 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2759 | |
3464 | |
2760 | static void stdin_ready (int revents, void *arg) |
3465 | static void stdin_ready (int revents, void *arg) |
2761 | { |
3466 | { |
2762 | if (revents & EV_READ) |
3467 | if (revents & EV_READ) |
2763 | /* stdin might have data for us, joy! */; |
3468 | /* stdin might have data for us, joy! */; |
2764 | else if (revents & EV_TIMEOUT) |
3469 | else if (revents & EV_TIMER) |
2765 | /* doh, nothing entered */; |
3470 | /* doh, nothing entered */; |
2766 | } |
3471 | } |
2767 | |
3472 | |
2768 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3473 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2769 | |
3474 | |
2770 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2771 | |
|
|
2772 | Feeds the given event set into the event loop, as if the specified event |
|
|
2773 | had happened for the specified watcher (which must be a pointer to an |
|
|
2774 | initialised but not necessarily started event watcher). |
|
|
2775 | |
|
|
2776 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3475 | =item ev_feed_fd_event (loop, int fd, int revents) |
2777 | |
3476 | |
2778 | Feed an event on the given fd, as if a file descriptor backend detected |
3477 | Feed an event on the given fd, as if a file descriptor backend detected |
2779 | the given events it. |
3478 | the given events it. |
2780 | |
3479 | |
2781 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3480 | =item ev_feed_signal_event (loop, int signum) |
2782 | |
3481 | |
2783 | Feed an event as if the given signal occurred (C<loop> must be the default |
3482 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
2784 | loop!). |
3483 | which is async-safe. |
2785 | |
3484 | |
2786 | =back |
3485 | =back |
|
|
3486 | |
|
|
3487 | |
|
|
3488 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3489 | |
|
|
3490 | This section explains some common idioms that are not immediately |
|
|
3491 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3492 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3493 | |
|
|
3494 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3495 | |
|
|
3496 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3497 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3498 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3499 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3500 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3501 | data: |
|
|
3502 | |
|
|
3503 | struct my_io |
|
|
3504 | { |
|
|
3505 | ev_io io; |
|
|
3506 | int otherfd; |
|
|
3507 | void *somedata; |
|
|
3508 | struct whatever *mostinteresting; |
|
|
3509 | }; |
|
|
3510 | |
|
|
3511 | ... |
|
|
3512 | struct my_io w; |
|
|
3513 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3514 | |
|
|
3515 | And since your callback will be called with a pointer to the watcher, you |
|
|
3516 | can cast it back to your own type: |
|
|
3517 | |
|
|
3518 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3519 | { |
|
|
3520 | struct my_io *w = (struct my_io *)w_; |
|
|
3521 | ... |
|
|
3522 | } |
|
|
3523 | |
|
|
3524 | More interesting and less C-conformant ways of casting your callback |
|
|
3525 | function type instead have been omitted. |
|
|
3526 | |
|
|
3527 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3528 | |
|
|
3529 | Another common scenario is to use some data structure with multiple |
|
|
3530 | embedded watchers, in effect creating your own watcher that combines |
|
|
3531 | multiple libev event sources into one "super-watcher": |
|
|
3532 | |
|
|
3533 | struct my_biggy |
|
|
3534 | { |
|
|
3535 | int some_data; |
|
|
3536 | ev_timer t1; |
|
|
3537 | ev_timer t2; |
|
|
3538 | } |
|
|
3539 | |
|
|
3540 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3541 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3542 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3543 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3544 | real programmers): |
|
|
3545 | |
|
|
3546 | #include <stddef.h> |
|
|
3547 | |
|
|
3548 | static void |
|
|
3549 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3550 | { |
|
|
3551 | struct my_biggy big = (struct my_biggy *) |
|
|
3552 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3553 | } |
|
|
3554 | |
|
|
3555 | static void |
|
|
3556 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3557 | { |
|
|
3558 | struct my_biggy big = (struct my_biggy *) |
|
|
3559 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3560 | } |
|
|
3561 | |
|
|
3562 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3563 | |
|
|
3564 | Often (especially in GUI toolkits) there are places where you have |
|
|
3565 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3566 | invoking C<ev_run>. |
|
|
3567 | |
|
|
3568 | This brings the problem of exiting - a callback might want to finish the |
|
|
3569 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3570 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3571 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3572 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3573 | |
|
|
3574 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3575 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3576 | triggered, using C<EVRUN_ONCE>: |
|
|
3577 | |
|
|
3578 | // main loop |
|
|
3579 | int exit_main_loop = 0; |
|
|
3580 | |
|
|
3581 | while (!exit_main_loop) |
|
|
3582 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3583 | |
|
|
3584 | // in a model watcher |
|
|
3585 | int exit_nested_loop = 0; |
|
|
3586 | |
|
|
3587 | while (!exit_nested_loop) |
|
|
3588 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3589 | |
|
|
3590 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3591 | |
|
|
3592 | // exit modal loop |
|
|
3593 | exit_nested_loop = 1; |
|
|
3594 | |
|
|
3595 | // exit main program, after modal loop is finished |
|
|
3596 | exit_main_loop = 1; |
|
|
3597 | |
|
|
3598 | // exit both |
|
|
3599 | exit_main_loop = exit_nested_loop = 1; |
|
|
3600 | |
|
|
3601 | =head2 THREAD LOCKING EXAMPLE |
|
|
3602 | |
|
|
3603 | Here is a fictitious example of how to run an event loop in a different |
|
|
3604 | thread from where callbacks are being invoked and watchers are |
|
|
3605 | created/added/removed. |
|
|
3606 | |
|
|
3607 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3608 | which uses exactly this technique (which is suited for many high-level |
|
|
3609 | languages). |
|
|
3610 | |
|
|
3611 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3612 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3613 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3614 | |
|
|
3615 | First, you need to associate some data with the event loop: |
|
|
3616 | |
|
|
3617 | typedef struct { |
|
|
3618 | mutex_t lock; /* global loop lock */ |
|
|
3619 | ev_async async_w; |
|
|
3620 | thread_t tid; |
|
|
3621 | cond_t invoke_cv; |
|
|
3622 | } userdata; |
|
|
3623 | |
|
|
3624 | void prepare_loop (EV_P) |
|
|
3625 | { |
|
|
3626 | // for simplicity, we use a static userdata struct. |
|
|
3627 | static userdata u; |
|
|
3628 | |
|
|
3629 | ev_async_init (&u->async_w, async_cb); |
|
|
3630 | ev_async_start (EV_A_ &u->async_w); |
|
|
3631 | |
|
|
3632 | pthread_mutex_init (&u->lock, 0); |
|
|
3633 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3634 | |
|
|
3635 | // now associate this with the loop |
|
|
3636 | ev_set_userdata (EV_A_ u); |
|
|
3637 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3638 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3639 | |
|
|
3640 | // then create the thread running ev_run |
|
|
3641 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3642 | } |
|
|
3643 | |
|
|
3644 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3645 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3646 | that might have been added: |
|
|
3647 | |
|
|
3648 | static void |
|
|
3649 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3650 | { |
|
|
3651 | // just used for the side effects |
|
|
3652 | } |
|
|
3653 | |
|
|
3654 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3655 | protecting the loop data, respectively. |
|
|
3656 | |
|
|
3657 | static void |
|
|
3658 | l_release (EV_P) |
|
|
3659 | { |
|
|
3660 | userdata *u = ev_userdata (EV_A); |
|
|
3661 | pthread_mutex_unlock (&u->lock); |
|
|
3662 | } |
|
|
3663 | |
|
|
3664 | static void |
|
|
3665 | l_acquire (EV_P) |
|
|
3666 | { |
|
|
3667 | userdata *u = ev_userdata (EV_A); |
|
|
3668 | pthread_mutex_lock (&u->lock); |
|
|
3669 | } |
|
|
3670 | |
|
|
3671 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3672 | into C<ev_run>: |
|
|
3673 | |
|
|
3674 | void * |
|
|
3675 | l_run (void *thr_arg) |
|
|
3676 | { |
|
|
3677 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3678 | |
|
|
3679 | l_acquire (EV_A); |
|
|
3680 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3681 | ev_run (EV_A_ 0); |
|
|
3682 | l_release (EV_A); |
|
|
3683 | |
|
|
3684 | return 0; |
|
|
3685 | } |
|
|
3686 | |
|
|
3687 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3688 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3689 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3690 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3691 | and b) skipping inter-thread-communication when there are no pending |
|
|
3692 | watchers is very beneficial): |
|
|
3693 | |
|
|
3694 | static void |
|
|
3695 | l_invoke (EV_P) |
|
|
3696 | { |
|
|
3697 | userdata *u = ev_userdata (EV_A); |
|
|
3698 | |
|
|
3699 | while (ev_pending_count (EV_A)) |
|
|
3700 | { |
|
|
3701 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3702 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3703 | } |
|
|
3704 | } |
|
|
3705 | |
|
|
3706 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3707 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3708 | thread to continue: |
|
|
3709 | |
|
|
3710 | static void |
|
|
3711 | real_invoke_pending (EV_P) |
|
|
3712 | { |
|
|
3713 | userdata *u = ev_userdata (EV_A); |
|
|
3714 | |
|
|
3715 | pthread_mutex_lock (&u->lock); |
|
|
3716 | ev_invoke_pending (EV_A); |
|
|
3717 | pthread_cond_signal (&u->invoke_cv); |
|
|
3718 | pthread_mutex_unlock (&u->lock); |
|
|
3719 | } |
|
|
3720 | |
|
|
3721 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3722 | event loop, you will now have to lock: |
|
|
3723 | |
|
|
3724 | ev_timer timeout_watcher; |
|
|
3725 | userdata *u = ev_userdata (EV_A); |
|
|
3726 | |
|
|
3727 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3728 | |
|
|
3729 | pthread_mutex_lock (&u->lock); |
|
|
3730 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3731 | ev_async_send (EV_A_ &u->async_w); |
|
|
3732 | pthread_mutex_unlock (&u->lock); |
|
|
3733 | |
|
|
3734 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3735 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3736 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3737 | watchers in the next event loop iteration. |
|
|
3738 | |
|
|
3739 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3740 | |
|
|
3741 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3742 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3743 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3744 | doesn't need callbacks anymore. |
|
|
3745 | |
|
|
3746 | Imagine you have coroutines that you can switch to using a function |
|
|
3747 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3748 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3749 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3750 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3751 | the differing C<;> conventions): |
|
|
3752 | |
|
|
3753 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3754 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3755 | |
|
|
3756 | That means instead of having a C callback function, you store the |
|
|
3757 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3758 | your callback, you instead have it switch to that coroutine. |
|
|
3759 | |
|
|
3760 | A coroutine might now wait for an event with a function called |
|
|
3761 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3762 | matter when, or whether the watcher is active or not when this function is |
|
|
3763 | called): |
|
|
3764 | |
|
|
3765 | void |
|
|
3766 | wait_for_event (ev_watcher *w) |
|
|
3767 | { |
|
|
3768 | ev_cb_set (w) = current_coro; |
|
|
3769 | switch_to (libev_coro); |
|
|
3770 | } |
|
|
3771 | |
|
|
3772 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3773 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3774 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3775 | |
|
|
3776 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3777 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3778 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3779 | any waiters. |
|
|
3780 | |
|
|
3781 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3782 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3783 | |
|
|
3784 | // my_ev.h |
|
|
3785 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3786 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3787 | #include "../libev/ev.h" |
|
|
3788 | |
|
|
3789 | // my_ev.c |
|
|
3790 | #define EV_H "my_ev.h" |
|
|
3791 | #include "../libev/ev.c" |
|
|
3792 | |
|
|
3793 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3794 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3795 | can even use F<ev.h> as header file name directly. |
2787 | |
3796 | |
2788 | |
3797 | |
2789 | =head1 LIBEVENT EMULATION |
3798 | =head1 LIBEVENT EMULATION |
2790 | |
3799 | |
2791 | Libev offers a compatibility emulation layer for libevent. It cannot |
3800 | Libev offers a compatibility emulation layer for libevent. It cannot |
2792 | emulate the internals of libevent, so here are some usage hints: |
3801 | emulate the internals of libevent, so here are some usage hints: |
2793 | |
3802 | |
2794 | =over 4 |
3803 | =over 4 |
|
|
3804 | |
|
|
3805 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3806 | |
|
|
3807 | This was the newest libevent version available when libev was implemented, |
|
|
3808 | and is still mostly unchanged in 2010. |
2795 | |
3809 | |
2796 | =item * Use it by including <event.h>, as usual. |
3810 | =item * Use it by including <event.h>, as usual. |
2797 | |
3811 | |
2798 | =item * The following members are fully supported: ev_base, ev_callback, |
3812 | =item * The following members are fully supported: ev_base, ev_callback, |
2799 | ev_arg, ev_fd, ev_res, ev_events. |
3813 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2805 | =item * Priorities are not currently supported. Initialising priorities |
3819 | =item * Priorities are not currently supported. Initialising priorities |
2806 | will fail and all watchers will have the same priority, even though there |
3820 | will fail and all watchers will have the same priority, even though there |
2807 | is an ev_pri field. |
3821 | is an ev_pri field. |
2808 | |
3822 | |
2809 | =item * In libevent, the last base created gets the signals, in libev, the |
3823 | =item * In libevent, the last base created gets the signals, in libev, the |
2810 | first base created (== the default loop) gets the signals. |
3824 | base that registered the signal gets the signals. |
2811 | |
3825 | |
2812 | =item * Other members are not supported. |
3826 | =item * Other members are not supported. |
2813 | |
3827 | |
2814 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3828 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2815 | to use the libev header file and library. |
3829 | to use the libev header file and library. |
… | |
… | |
2834 | Care has been taken to keep the overhead low. The only data member the C++ |
3848 | Care has been taken to keep the overhead low. The only data member the C++ |
2835 | classes add (compared to plain C-style watchers) is the event loop pointer |
3849 | classes add (compared to plain C-style watchers) is the event loop pointer |
2836 | that the watcher is associated with (or no additional members at all if |
3850 | that the watcher is associated with (or no additional members at all if |
2837 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3851 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2838 | |
3852 | |
2839 | Currently, functions, and static and non-static member functions can be |
3853 | Currently, functions, static and non-static member functions and classes |
2840 | used as callbacks. Other types should be easy to add as long as they only |
3854 | with C<operator ()> can be used as callbacks. Other types should be easy |
2841 | need one additional pointer for context. If you need support for other |
3855 | to add as long as they only need one additional pointer for context. If |
2842 | types of functors please contact the author (preferably after implementing |
3856 | you need support for other types of functors please contact the author |
2843 | it). |
3857 | (preferably after implementing it). |
2844 | |
3858 | |
2845 | Here is a list of things available in the C<ev> namespace: |
3859 | Here is a list of things available in the C<ev> namespace: |
2846 | |
3860 | |
2847 | =over 4 |
3861 | =over 4 |
2848 | |
3862 | |
… | |
… | |
2866 | |
3880 | |
2867 | =over 4 |
3881 | =over 4 |
2868 | |
3882 | |
2869 | =item ev::TYPE::TYPE () |
3883 | =item ev::TYPE::TYPE () |
2870 | |
3884 | |
2871 | =item ev::TYPE::TYPE (struct ev_loop *) |
3885 | =item ev::TYPE::TYPE (loop) |
2872 | |
3886 | |
2873 | =item ev::TYPE::~TYPE |
3887 | =item ev::TYPE::~TYPE |
2874 | |
3888 | |
2875 | The constructor (optionally) takes an event loop to associate the watcher |
3889 | The constructor (optionally) takes an event loop to associate the watcher |
2876 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3890 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2909 | myclass obj; |
3923 | myclass obj; |
2910 | ev::io iow; |
3924 | ev::io iow; |
2911 | iow.set <myclass, &myclass::io_cb> (&obj); |
3925 | iow.set <myclass, &myclass::io_cb> (&obj); |
2912 | |
3926 | |
2913 | =item w->set (object *) |
3927 | =item w->set (object *) |
2914 | |
|
|
2915 | This is an B<experimental> feature that might go away in a future version. |
|
|
2916 | |
3928 | |
2917 | This is a variation of a method callback - leaving out the method to call |
3929 | This is a variation of a method callback - leaving out the method to call |
2918 | will default the method to C<operator ()>, which makes it possible to use |
3930 | will default the method to C<operator ()>, which makes it possible to use |
2919 | functor objects without having to manually specify the C<operator ()> all |
3931 | functor objects without having to manually specify the C<operator ()> all |
2920 | the time. Incidentally, you can then also leave out the template argument |
3932 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
2953 | Example: Use a plain function as callback. |
3965 | Example: Use a plain function as callback. |
2954 | |
3966 | |
2955 | static void io_cb (ev::io &w, int revents) { } |
3967 | static void io_cb (ev::io &w, int revents) { } |
2956 | iow.set <io_cb> (); |
3968 | iow.set <io_cb> (); |
2957 | |
3969 | |
2958 | =item w->set (struct ev_loop *) |
3970 | =item w->set (loop) |
2959 | |
3971 | |
2960 | Associates a different C<struct ev_loop> with this watcher. You can only |
3972 | Associates a different C<struct ev_loop> with this watcher. You can only |
2961 | do this when the watcher is inactive (and not pending either). |
3973 | do this when the watcher is inactive (and not pending either). |
2962 | |
3974 | |
2963 | =item w->set ([arguments]) |
3975 | =item w->set ([arguments]) |
2964 | |
3976 | |
2965 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3977 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2966 | called at least once. Unlike the C counterpart, an active watcher gets |
3978 | method or a suitable start method must be called at least once. Unlike the |
2967 | automatically stopped and restarted when reconfiguring it with this |
3979 | C counterpart, an active watcher gets automatically stopped and restarted |
2968 | method. |
3980 | when reconfiguring it with this method. |
2969 | |
3981 | |
2970 | =item w->start () |
3982 | =item w->start () |
2971 | |
3983 | |
2972 | Starts the watcher. Note that there is no C<loop> argument, as the |
3984 | Starts the watcher. Note that there is no C<loop> argument, as the |
2973 | constructor already stores the event loop. |
3985 | constructor already stores the event loop. |
2974 | |
3986 | |
|
|
3987 | =item w->start ([arguments]) |
|
|
3988 | |
|
|
3989 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3990 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3991 | the configure C<set> method of the watcher. |
|
|
3992 | |
2975 | =item w->stop () |
3993 | =item w->stop () |
2976 | |
3994 | |
2977 | Stops the watcher if it is active. Again, no C<loop> argument. |
3995 | Stops the watcher if it is active. Again, no C<loop> argument. |
2978 | |
3996 | |
2979 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3997 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2991 | |
4009 | |
2992 | =back |
4010 | =back |
2993 | |
4011 | |
2994 | =back |
4012 | =back |
2995 | |
4013 | |
2996 | Example: Define a class with an IO and idle watcher, start one of them in |
4014 | Example: Define a class with two I/O and idle watchers, start the I/O |
2997 | the constructor. |
4015 | watchers in the constructor. |
2998 | |
4016 | |
2999 | class myclass |
4017 | class myclass |
3000 | { |
4018 | { |
3001 | ev::io io ; void io_cb (ev::io &w, int revents); |
4019 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4020 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3002 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4021 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3003 | |
4022 | |
3004 | myclass (int fd) |
4023 | myclass (int fd) |
3005 | { |
4024 | { |
3006 | io .set <myclass, &myclass::io_cb > (this); |
4025 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4026 | io2 .set <myclass, &myclass::io2_cb > (this); |
3007 | idle.set <myclass, &myclass::idle_cb> (this); |
4027 | idle.set <myclass, &myclass::idle_cb> (this); |
3008 | |
4028 | |
3009 | io.start (fd, ev::READ); |
4029 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4030 | io.start (); // start it whenever convenient |
|
|
4031 | |
|
|
4032 | io2.start (fd, ev::READ); // set + start in one call |
3010 | } |
4033 | } |
3011 | }; |
4034 | }; |
3012 | |
4035 | |
3013 | |
4036 | |
3014 | =head1 OTHER LANGUAGE BINDINGS |
4037 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3053 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4076 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3054 | |
4077 | |
3055 | =item D |
4078 | =item D |
3056 | |
4079 | |
3057 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4080 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3058 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4081 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3059 | |
4082 | |
3060 | =item Ocaml |
4083 | =item Ocaml |
3061 | |
4084 | |
3062 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4085 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3063 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4086 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4087 | |
|
|
4088 | =item Lua |
|
|
4089 | |
|
|
4090 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4091 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4092 | L<http://github.com/brimworks/lua-ev>. |
3064 | |
4093 | |
3065 | =back |
4094 | =back |
3066 | |
4095 | |
3067 | |
4096 | |
3068 | =head1 MACRO MAGIC |
4097 | =head1 MACRO MAGIC |
… | |
… | |
3082 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4111 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3083 | C<EV_A_> is used when other arguments are following. Example: |
4112 | C<EV_A_> is used when other arguments are following. Example: |
3084 | |
4113 | |
3085 | ev_unref (EV_A); |
4114 | ev_unref (EV_A); |
3086 | ev_timer_add (EV_A_ watcher); |
4115 | ev_timer_add (EV_A_ watcher); |
3087 | ev_loop (EV_A_ 0); |
4116 | ev_run (EV_A_ 0); |
3088 | |
4117 | |
3089 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4118 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3090 | which is often provided by the following macro. |
4119 | which is often provided by the following macro. |
3091 | |
4120 | |
3092 | =item C<EV_P>, C<EV_P_> |
4121 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3105 | suitable for use with C<EV_A>. |
4134 | suitable for use with C<EV_A>. |
3106 | |
4135 | |
3107 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4136 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3108 | |
4137 | |
3109 | Similar to the other two macros, this gives you the value of the default |
4138 | Similar to the other two macros, this gives you the value of the default |
3110 | loop, if multiple loops are supported ("ev loop default"). |
4139 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4140 | will be initialised if it isn't already initialised. |
|
|
4141 | |
|
|
4142 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4143 | to initialise the loop somewhere. |
3111 | |
4144 | |
3112 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4145 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3113 | |
4146 | |
3114 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4147 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3115 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4148 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3132 | } |
4165 | } |
3133 | |
4166 | |
3134 | ev_check check; |
4167 | ev_check check; |
3135 | ev_check_init (&check, check_cb); |
4168 | ev_check_init (&check, check_cb); |
3136 | ev_check_start (EV_DEFAULT_ &check); |
4169 | ev_check_start (EV_DEFAULT_ &check); |
3137 | ev_loop (EV_DEFAULT_ 0); |
4170 | ev_run (EV_DEFAULT_ 0); |
3138 | |
4171 | |
3139 | =head1 EMBEDDING |
4172 | =head1 EMBEDDING |
3140 | |
4173 | |
3141 | Libev can (and often is) directly embedded into host |
4174 | Libev can (and often is) directly embedded into host |
3142 | applications. Examples of applications that embed it include the Deliantra |
4175 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3222 | libev.m4 |
4255 | libev.m4 |
3223 | |
4256 | |
3224 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4257 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3225 | |
4258 | |
3226 | Libev can be configured via a variety of preprocessor symbols you have to |
4259 | Libev can be configured via a variety of preprocessor symbols you have to |
3227 | define before including any of its files. The default in the absence of |
4260 | define before including (or compiling) any of its files. The default in |
3228 | autoconf is documented for every option. |
4261 | the absence of autoconf is documented for every option. |
|
|
4262 | |
|
|
4263 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4264 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4265 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4266 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4267 | users of libev and the libev code itself must be compiled with compatible |
|
|
4268 | settings. |
3229 | |
4269 | |
3230 | =over 4 |
4270 | =over 4 |
3231 | |
4271 | |
|
|
4272 | =item EV_COMPAT3 (h) |
|
|
4273 | |
|
|
4274 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4275 | release of libev comes with wrappers for the functions and symbols that |
|
|
4276 | have been renamed between libev version 3 and 4. |
|
|
4277 | |
|
|
4278 | You can disable these wrappers (to test compatibility with future |
|
|
4279 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4280 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4281 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4282 | typedef in that case. |
|
|
4283 | |
|
|
4284 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4285 | and in some even more future version the compatibility code will be |
|
|
4286 | removed completely. |
|
|
4287 | |
3232 | =item EV_STANDALONE |
4288 | =item EV_STANDALONE (h) |
3233 | |
4289 | |
3234 | Must always be C<1> if you do not use autoconf configuration, which |
4290 | Must always be C<1> if you do not use autoconf configuration, which |
3235 | keeps libev from including F<config.h>, and it also defines dummy |
4291 | keeps libev from including F<config.h>, and it also defines dummy |
3236 | implementations for some libevent functions (such as logging, which is not |
4292 | implementations for some libevent functions (such as logging, which is not |
3237 | supported). It will also not define any of the structs usually found in |
4293 | supported). It will also not define any of the structs usually found in |
3238 | F<event.h> that are not directly supported by the libev core alone. |
4294 | F<event.h> that are not directly supported by the libev core alone. |
3239 | |
4295 | |
3240 | In stanbdalone mode, libev will still try to automatically deduce the |
4296 | In standalone mode, libev will still try to automatically deduce the |
3241 | configuration, but has to be more conservative. |
4297 | configuration, but has to be more conservative. |
|
|
4298 | |
|
|
4299 | =item EV_USE_FLOOR |
|
|
4300 | |
|
|
4301 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4302 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4303 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4304 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4305 | function is not available will fail, so the safe default is to not enable |
|
|
4306 | this. |
3242 | |
4307 | |
3243 | =item EV_USE_MONOTONIC |
4308 | =item EV_USE_MONOTONIC |
3244 | |
4309 | |
3245 | If defined to be C<1>, libev will try to detect the availability of the |
4310 | If defined to be C<1>, libev will try to detect the availability of the |
3246 | monotonic clock option at both compile time and runtime. Otherwise no |
4311 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3310 | be used is the winsock select). This means that it will call |
4375 | be used is the winsock select). This means that it will call |
3311 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4376 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3312 | it is assumed that all these functions actually work on fds, even |
4377 | it is assumed that all these functions actually work on fds, even |
3313 | on win32. Should not be defined on non-win32 platforms. |
4378 | on win32. Should not be defined on non-win32 platforms. |
3314 | |
4379 | |
3315 | =item EV_FD_TO_WIN32_HANDLE |
4380 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3316 | |
4381 | |
3317 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4382 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3318 | file descriptors to socket handles. When not defining this symbol (the |
4383 | file descriptors to socket handles. When not defining this symbol (the |
3319 | default), then libev will call C<_get_osfhandle>, which is usually |
4384 | default), then libev will call C<_get_osfhandle>, which is usually |
3320 | correct. In some cases, programs use their own file descriptor management, |
4385 | correct. In some cases, programs use their own file descriptor management, |
3321 | in which case they can provide this function to map fds to socket handles. |
4386 | in which case they can provide this function to map fds to socket handles. |
|
|
4387 | |
|
|
4388 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4389 | |
|
|
4390 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4391 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4392 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4393 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4394 | |
|
|
4395 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4396 | |
|
|
4397 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4398 | macro can be used to override the C<close> function, useful to unregister |
|
|
4399 | file descriptors again. Note that the replacement function has to close |
|
|
4400 | the underlying OS handle. |
3322 | |
4401 | |
3323 | =item EV_USE_POLL |
4402 | =item EV_USE_POLL |
3324 | |
4403 | |
3325 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4404 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3326 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4405 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3365 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4444 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3366 | |
4445 | |
3367 | =item EV_ATOMIC_T |
4446 | =item EV_ATOMIC_T |
3368 | |
4447 | |
3369 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4448 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3370 | access is atomic with respect to other threads or signal contexts. No such |
4449 | access is atomic and serialised with respect to other threads or signal |
3371 | type is easily found in the C language, so you can provide your own type |
4450 | contexts. No such type is easily found in the C language, so you can |
3372 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4451 | provide your own type that you know is safe for your purposes. It is used |
3373 | as well as for signal and thread safety in C<ev_async> watchers. |
4452 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4453 | in C<ev_async> watchers. |
3374 | |
4454 | |
3375 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4455 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3376 | (from F<signal.h>), which is usually good enough on most platforms. |
4456 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4457 | although strictly speaking using a type that also implies a memory fence |
|
|
4458 | is required. |
3377 | |
4459 | |
3378 | =item EV_H |
4460 | =item EV_H (h) |
3379 | |
4461 | |
3380 | The name of the F<ev.h> header file used to include it. The default if |
4462 | The name of the F<ev.h> header file used to include it. The default if |
3381 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4463 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3382 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4464 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3383 | |
4465 | |
3384 | =item EV_CONFIG_H |
4466 | =item EV_CONFIG_H (h) |
3385 | |
4467 | |
3386 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4468 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3387 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4469 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3388 | C<EV_H>, above. |
4470 | C<EV_H>, above. |
3389 | |
4471 | |
3390 | =item EV_EVENT_H |
4472 | =item EV_EVENT_H (h) |
3391 | |
4473 | |
3392 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4474 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3393 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4475 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3394 | |
4476 | |
3395 | =item EV_PROTOTYPES |
4477 | =item EV_PROTOTYPES (h) |
3396 | |
4478 | |
3397 | If defined to be C<0>, then F<ev.h> will not define any function |
4479 | If defined to be C<0>, then F<ev.h> will not define any function |
3398 | prototypes, but still define all the structs and other symbols. This is |
4480 | prototypes, but still define all the structs and other symbols. This is |
3399 | occasionally useful if you want to provide your own wrapper functions |
4481 | occasionally useful if you want to provide your own wrapper functions |
3400 | around libev functions. |
4482 | around libev functions. |
… | |
… | |
3405 | will have the C<struct ev_loop *> as first argument, and you can create |
4487 | will have the C<struct ev_loop *> as first argument, and you can create |
3406 | additional independent event loops. Otherwise there will be no support |
4488 | additional independent event loops. Otherwise there will be no support |
3407 | for multiple event loops and there is no first event loop pointer |
4489 | for multiple event loops and there is no first event loop pointer |
3408 | argument. Instead, all functions act on the single default loop. |
4490 | argument. Instead, all functions act on the single default loop. |
3409 | |
4491 | |
|
|
4492 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4493 | default loop when multiplicity is switched off - you always have to |
|
|
4494 | initialise the loop manually in this case. |
|
|
4495 | |
3410 | =item EV_MINPRI |
4496 | =item EV_MINPRI |
3411 | |
4497 | |
3412 | =item EV_MAXPRI |
4498 | =item EV_MAXPRI |
3413 | |
4499 | |
3414 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4500 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3422 | fine. |
4508 | fine. |
3423 | |
4509 | |
3424 | If your embedding application does not need any priorities, defining these |
4510 | If your embedding application does not need any priorities, defining these |
3425 | both to C<0> will save some memory and CPU. |
4511 | both to C<0> will save some memory and CPU. |
3426 | |
4512 | |
3427 | =item EV_PERIODIC_ENABLE |
4513 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4514 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4515 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3428 | |
4516 | |
3429 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4517 | If undefined or defined to be C<1> (and the platform supports it), then |
3430 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4518 | the respective watcher type is supported. If defined to be C<0>, then it |
3431 | code. |
4519 | is not. Disabling watcher types mainly saves code size. |
3432 | |
4520 | |
3433 | =item EV_IDLE_ENABLE |
4521 | =item EV_FEATURES |
3434 | |
|
|
3435 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3436 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3437 | code. |
|
|
3438 | |
|
|
3439 | =item EV_EMBED_ENABLE |
|
|
3440 | |
|
|
3441 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3442 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3443 | watcher types, which therefore must not be disabled. |
|
|
3444 | |
|
|
3445 | =item EV_STAT_ENABLE |
|
|
3446 | |
|
|
3447 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3448 | defined to be C<0>, then they are not. |
|
|
3449 | |
|
|
3450 | =item EV_FORK_ENABLE |
|
|
3451 | |
|
|
3452 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3453 | defined to be C<0>, then they are not. |
|
|
3454 | |
|
|
3455 | =item EV_ASYNC_ENABLE |
|
|
3456 | |
|
|
3457 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3458 | defined to be C<0>, then they are not. |
|
|
3459 | |
|
|
3460 | =item EV_MINIMAL |
|
|
3461 | |
4522 | |
3462 | If you need to shave off some kilobytes of code at the expense of some |
4523 | If you need to shave off some kilobytes of code at the expense of some |
3463 | speed, define this symbol to C<1>. Currently this is used to override some |
4524 | speed (but with the full API), you can define this symbol to request |
3464 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4525 | certain subsets of functionality. The default is to enable all features |
3465 | much smaller 2-heap for timer management over the default 4-heap. |
4526 | that can be enabled on the platform. |
|
|
4527 | |
|
|
4528 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4529 | with some broad features you want) and then selectively re-enable |
|
|
4530 | additional parts you want, for example if you want everything minimal, |
|
|
4531 | but multiple event loop support, async and child watchers and the poll |
|
|
4532 | backend, use this: |
|
|
4533 | |
|
|
4534 | #define EV_FEATURES 0 |
|
|
4535 | #define EV_MULTIPLICITY 1 |
|
|
4536 | #define EV_USE_POLL 1 |
|
|
4537 | #define EV_CHILD_ENABLE 1 |
|
|
4538 | #define EV_ASYNC_ENABLE 1 |
|
|
4539 | |
|
|
4540 | The actual value is a bitset, it can be a combination of the following |
|
|
4541 | values: |
|
|
4542 | |
|
|
4543 | =over 4 |
|
|
4544 | |
|
|
4545 | =item C<1> - faster/larger code |
|
|
4546 | |
|
|
4547 | Use larger code to speed up some operations. |
|
|
4548 | |
|
|
4549 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4550 | code size by roughly 30% on amd64). |
|
|
4551 | |
|
|
4552 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4553 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4554 | assertions. |
|
|
4555 | |
|
|
4556 | =item C<2> - faster/larger data structures |
|
|
4557 | |
|
|
4558 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4559 | hash table sizes and so on. This will usually further increase code size |
|
|
4560 | and can additionally have an effect on the size of data structures at |
|
|
4561 | runtime. |
|
|
4562 | |
|
|
4563 | =item C<4> - full API configuration |
|
|
4564 | |
|
|
4565 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4566 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4567 | |
|
|
4568 | =item C<8> - full API |
|
|
4569 | |
|
|
4570 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4571 | details on which parts of the API are still available without this |
|
|
4572 | feature, and do not complain if this subset changes over time. |
|
|
4573 | |
|
|
4574 | =item C<16> - enable all optional watcher types |
|
|
4575 | |
|
|
4576 | Enables all optional watcher types. If you want to selectively enable |
|
|
4577 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4578 | embed, async, child...) you can enable them manually by defining |
|
|
4579 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4580 | |
|
|
4581 | =item C<32> - enable all backends |
|
|
4582 | |
|
|
4583 | This enables all backends - without this feature, you need to enable at |
|
|
4584 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4585 | |
|
|
4586 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4587 | |
|
|
4588 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4589 | default. |
|
|
4590 | |
|
|
4591 | =back |
|
|
4592 | |
|
|
4593 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4594 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4595 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4596 | watchers, timers and monotonic clock support. |
|
|
4597 | |
|
|
4598 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4599 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4600 | your program might be left out as well - a binary starting a timer and an |
|
|
4601 | I/O watcher then might come out at only 5Kb. |
|
|
4602 | |
|
|
4603 | =item EV_AVOID_STDIO |
|
|
4604 | |
|
|
4605 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4606 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4607 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4608 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4609 | big. |
|
|
4610 | |
|
|
4611 | Note that error messages might become less precise when this option is |
|
|
4612 | enabled. |
|
|
4613 | |
|
|
4614 | =item EV_NSIG |
|
|
4615 | |
|
|
4616 | The highest supported signal number, +1 (or, the number of |
|
|
4617 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4618 | automatically, but sometimes this fails, in which case it can be |
|
|
4619 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4620 | good for about any system in existence) can save some memory, as libev |
|
|
4621 | statically allocates some 12-24 bytes per signal number. |
3466 | |
4622 | |
3467 | =item EV_PID_HASHSIZE |
4623 | =item EV_PID_HASHSIZE |
3468 | |
4624 | |
3469 | C<ev_child> watchers use a small hash table to distribute workload by |
4625 | C<ev_child> watchers use a small hash table to distribute workload by |
3470 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4626 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3471 | than enough. If you need to manage thousands of children you might want to |
4627 | usually more than enough. If you need to manage thousands of children you |
3472 | increase this value (I<must> be a power of two). |
4628 | might want to increase this value (I<must> be a power of two). |
3473 | |
4629 | |
3474 | =item EV_INOTIFY_HASHSIZE |
4630 | =item EV_INOTIFY_HASHSIZE |
3475 | |
4631 | |
3476 | C<ev_stat> watchers use a small hash table to distribute workload by |
4632 | C<ev_stat> watchers use a small hash table to distribute workload by |
3477 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4633 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3478 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4634 | disabled), usually more than enough. If you need to manage thousands of |
3479 | watchers you might want to increase this value (I<must> be a power of |
4635 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3480 | two). |
4636 | power of two). |
3481 | |
4637 | |
3482 | =item EV_USE_4HEAP |
4638 | =item EV_USE_4HEAP |
3483 | |
4639 | |
3484 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4640 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3485 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4641 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3486 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4642 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3487 | faster performance with many (thousands) of watchers. |
4643 | faster performance with many (thousands) of watchers. |
3488 | |
4644 | |
3489 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4645 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3490 | (disabled). |
4646 | will be C<0>. |
3491 | |
4647 | |
3492 | =item EV_HEAP_CACHE_AT |
4648 | =item EV_HEAP_CACHE_AT |
3493 | |
4649 | |
3494 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4650 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3495 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4651 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3496 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4652 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3497 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4653 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3498 | but avoids random read accesses on heap changes. This improves performance |
4654 | but avoids random read accesses on heap changes. This improves performance |
3499 | noticeably with many (hundreds) of watchers. |
4655 | noticeably with many (hundreds) of watchers. |
3500 | |
4656 | |
3501 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4657 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3502 | (disabled). |
4658 | will be C<0>. |
3503 | |
4659 | |
3504 | =item EV_VERIFY |
4660 | =item EV_VERIFY |
3505 | |
4661 | |
3506 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4662 | Controls how much internal verification (see C<ev_verify ()>) will |
3507 | be done: If set to C<0>, no internal verification code will be compiled |
4663 | be done: If set to C<0>, no internal verification code will be compiled |
3508 | in. If set to C<1>, then verification code will be compiled in, but not |
4664 | in. If set to C<1>, then verification code will be compiled in, but not |
3509 | called. If set to C<2>, then the internal verification code will be |
4665 | called. If set to C<2>, then the internal verification code will be |
3510 | called once per loop, which can slow down libev. If set to C<3>, then the |
4666 | called once per loop, which can slow down libev. If set to C<3>, then the |
3511 | verification code will be called very frequently, which will slow down |
4667 | verification code will be called very frequently, which will slow down |
3512 | libev considerably. |
4668 | libev considerably. |
3513 | |
4669 | |
3514 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4670 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3515 | C<0>. |
4671 | will be C<0>. |
3516 | |
4672 | |
3517 | =item EV_COMMON |
4673 | =item EV_COMMON |
3518 | |
4674 | |
3519 | By default, all watchers have a C<void *data> member. By redefining |
4675 | By default, all watchers have a C<void *data> member. By redefining |
3520 | this macro to a something else you can include more and other types of |
4676 | this macro to something else you can include more and other types of |
3521 | members. You have to define it each time you include one of the files, |
4677 | members. You have to define it each time you include one of the files, |
3522 | though, and it must be identical each time. |
4678 | though, and it must be identical each time. |
3523 | |
4679 | |
3524 | For example, the perl EV module uses something like this: |
4680 | For example, the perl EV module uses something like this: |
3525 | |
4681 | |
… | |
… | |
3578 | file. |
4734 | file. |
3579 | |
4735 | |
3580 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4736 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3581 | that everybody includes and which overrides some configure choices: |
4737 | that everybody includes and which overrides some configure choices: |
3582 | |
4738 | |
3583 | #define EV_MINIMAL 1 |
4739 | #define EV_FEATURES 8 |
3584 | #define EV_USE_POLL 0 |
4740 | #define EV_USE_SELECT 1 |
3585 | #define EV_MULTIPLICITY 0 |
|
|
3586 | #define EV_PERIODIC_ENABLE 0 |
4741 | #define EV_PREPARE_ENABLE 1 |
|
|
4742 | #define EV_IDLE_ENABLE 1 |
3587 | #define EV_STAT_ENABLE 0 |
4743 | #define EV_SIGNAL_ENABLE 1 |
3588 | #define EV_FORK_ENABLE 0 |
4744 | #define EV_CHILD_ENABLE 1 |
|
|
4745 | #define EV_USE_STDEXCEPT 0 |
3589 | #define EV_CONFIG_H <config.h> |
4746 | #define EV_CONFIG_H <config.h> |
3590 | #define EV_MINPRI 0 |
|
|
3591 | #define EV_MAXPRI 0 |
|
|
3592 | |
4747 | |
3593 | #include "ev++.h" |
4748 | #include "ev++.h" |
3594 | |
4749 | |
3595 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4750 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3596 | |
4751 | |
3597 | #include "ev_cpp.h" |
4752 | #include "ev_cpp.h" |
3598 | #include "ev.c" |
4753 | #include "ev.c" |
3599 | |
4754 | |
3600 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4755 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3601 | |
4756 | |
3602 | =head2 THREADS AND COROUTINES |
4757 | =head2 THREADS AND COROUTINES |
3603 | |
4758 | |
3604 | =head3 THREADS |
4759 | =head3 THREADS |
3605 | |
4760 | |
… | |
… | |
3656 | default loop and triggering an C<ev_async> watcher from the default loop |
4811 | default loop and triggering an C<ev_async> watcher from the default loop |
3657 | watcher callback into the event loop interested in the signal. |
4812 | watcher callback into the event loop interested in the signal. |
3658 | |
4813 | |
3659 | =back |
4814 | =back |
3660 | |
4815 | |
|
|
4816 | See also L<THREAD LOCKING EXAMPLE>. |
|
|
4817 | |
3661 | =head3 COROUTINES |
4818 | =head3 COROUTINES |
3662 | |
4819 | |
3663 | Libev is very accommodating to coroutines ("cooperative threads"): |
4820 | Libev is very accommodating to coroutines ("cooperative threads"): |
3664 | libev fully supports nesting calls to its functions from different |
4821 | libev fully supports nesting calls to its functions from different |
3665 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4822 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3666 | different coroutines, and switch freely between both coroutines running the |
4823 | different coroutines, and switch freely between both coroutines running |
3667 | loop, as long as you don't confuse yourself). The only exception is that |
4824 | the loop, as long as you don't confuse yourself). The only exception is |
3668 | you must not do this from C<ev_periodic> reschedule callbacks. |
4825 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3669 | |
4826 | |
3670 | Care has been taken to ensure that libev does not keep local state inside |
4827 | Care has been taken to ensure that libev does not keep local state inside |
3671 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4828 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3672 | they do not call any callbacks. |
4829 | they do not call any callbacks. |
3673 | |
4830 | |
3674 | =head2 COMPILER WARNINGS |
4831 | =head2 COMPILER WARNINGS |
3675 | |
4832 | |
3676 | Depending on your compiler and compiler settings, you might get no or a |
4833 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
3687 | maintainable. |
4844 | maintainable. |
3688 | |
4845 | |
3689 | And of course, some compiler warnings are just plain stupid, or simply |
4846 | And of course, some compiler warnings are just plain stupid, or simply |
3690 | wrong (because they don't actually warn about the condition their message |
4847 | wrong (because they don't actually warn about the condition their message |
3691 | seems to warn about). For example, certain older gcc versions had some |
4848 | seems to warn about). For example, certain older gcc versions had some |
3692 | warnings that resulted an extreme number of false positives. These have |
4849 | warnings that resulted in an extreme number of false positives. These have |
3693 | been fixed, but some people still insist on making code warn-free with |
4850 | been fixed, but some people still insist on making code warn-free with |
3694 | such buggy versions. |
4851 | such buggy versions. |
3695 | |
4852 | |
3696 | While libev is written to generate as few warnings as possible, |
4853 | While libev is written to generate as few warnings as possible, |
3697 | "warn-free" code is not a goal, and it is recommended not to build libev |
4854 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3733 | I suggest using suppression lists. |
4890 | I suggest using suppression lists. |
3734 | |
4891 | |
3735 | |
4892 | |
3736 | =head1 PORTABILITY NOTES |
4893 | =head1 PORTABILITY NOTES |
3737 | |
4894 | |
|
|
4895 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4896 | |
|
|
4897 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4898 | interfaces but I<disables> them by default. |
|
|
4899 | |
|
|
4900 | That means that libev compiled in the default environment doesn't support |
|
|
4901 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4902 | |
|
|
4903 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4904 | by enabling the large file API, which makes them incompatible with the |
|
|
4905 | standard libev compiled for their system. |
|
|
4906 | |
|
|
4907 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4908 | suddenly make it incompatible to the default compile time environment, |
|
|
4909 | i.e. all programs not using special compile switches. |
|
|
4910 | |
|
|
4911 | =head2 OS/X AND DARWIN BUGS |
|
|
4912 | |
|
|
4913 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4914 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4915 | OpenGL drivers. |
|
|
4916 | |
|
|
4917 | =head3 C<kqueue> is buggy |
|
|
4918 | |
|
|
4919 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4920 | only sockets, many support pipes. |
|
|
4921 | |
|
|
4922 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4923 | rotten platform, but of course you can still ask for it when creating a |
|
|
4924 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4925 | probably going to work well. |
|
|
4926 | |
|
|
4927 | =head3 C<poll> is buggy |
|
|
4928 | |
|
|
4929 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4930 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4931 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4932 | |
|
|
4933 | Libev tries to work around this by not using C<poll> by default on |
|
|
4934 | this rotten platform, but of course you can still ask for it when creating |
|
|
4935 | a loop. |
|
|
4936 | |
|
|
4937 | =head3 C<select> is buggy |
|
|
4938 | |
|
|
4939 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4940 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4941 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4942 | you use more. |
|
|
4943 | |
|
|
4944 | There is an undocumented "workaround" for this - defining |
|
|
4945 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4946 | work on OS/X. |
|
|
4947 | |
|
|
4948 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4949 | |
|
|
4950 | =head3 C<errno> reentrancy |
|
|
4951 | |
|
|
4952 | The default compile environment on Solaris is unfortunately so |
|
|
4953 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4954 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4955 | defined by default. A valid, if stupid, implementation choice. |
|
|
4956 | |
|
|
4957 | If you want to use libev in threaded environments you have to make sure |
|
|
4958 | it's compiled with C<_REENTRANT> defined. |
|
|
4959 | |
|
|
4960 | =head3 Event port backend |
|
|
4961 | |
|
|
4962 | The scalable event interface for Solaris is called "event |
|
|
4963 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4964 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4965 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4966 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4967 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4968 | great. |
|
|
4969 | |
|
|
4970 | If you can't get it to work, you can try running the program by setting |
|
|
4971 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4972 | C<select> backends. |
|
|
4973 | |
|
|
4974 | =head2 AIX POLL BUG |
|
|
4975 | |
|
|
4976 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4977 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4978 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4979 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4980 | |
3738 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4981 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4982 | |
|
|
4983 | =head3 General issues |
3739 | |
4984 | |
3740 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4985 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3741 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4986 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3742 | model. Libev still offers limited functionality on this platform in |
4987 | model. Libev still offers limited functionality on this platform in |
3743 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4988 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3744 | descriptors. This only applies when using Win32 natively, not when using |
4989 | descriptors. This only applies when using Win32 natively, not when using |
3745 | e.g. cygwin. |
4990 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4991 | as every compiler comes with a slightly differently broken/incompatible |
|
|
4992 | environment. |
3746 | |
4993 | |
3747 | Lifting these limitations would basically require the full |
4994 | Lifting these limitations would basically require the full |
3748 | re-implementation of the I/O system. If you are into these kinds of |
4995 | re-implementation of the I/O system. If you are into this kind of thing, |
3749 | things, then note that glib does exactly that for you in a very portable |
4996 | then note that glib does exactly that for you in a very portable way (note |
3750 | way (note also that glib is the slowest event library known to man). |
4997 | also that glib is the slowest event library known to man). |
3751 | |
4998 | |
3752 | There is no supported compilation method available on windows except |
4999 | There is no supported compilation method available on windows except |
3753 | embedding it into other applications. |
5000 | embedding it into other applications. |
|
|
5001 | |
|
|
5002 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
5003 | tries its best, but under most conditions, signals will simply not work. |
3754 | |
5004 | |
3755 | Not a libev limitation but worth mentioning: windows apparently doesn't |
5005 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3756 | accept large writes: instead of resulting in a partial write, windows will |
5006 | accept large writes: instead of resulting in a partial write, windows will |
3757 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
5007 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3758 | so make sure you only write small amounts into your sockets (less than a |
5008 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3763 | the abysmal performance of winsockets, using a large number of sockets |
5013 | the abysmal performance of winsockets, using a large number of sockets |
3764 | is not recommended (and not reasonable). If your program needs to use |
5014 | is not recommended (and not reasonable). If your program needs to use |
3765 | more than a hundred or so sockets, then likely it needs to use a totally |
5015 | more than a hundred or so sockets, then likely it needs to use a totally |
3766 | different implementation for windows, as libev offers the POSIX readiness |
5016 | different implementation for windows, as libev offers the POSIX readiness |
3767 | notification model, which cannot be implemented efficiently on windows |
5017 | notification model, which cannot be implemented efficiently on windows |
3768 | (Microsoft monopoly games). |
5018 | (due to Microsoft monopoly games). |
3769 | |
5019 | |
3770 | A typical way to use libev under windows is to embed it (see the embedding |
5020 | A typical way to use libev under windows is to embed it (see the embedding |
3771 | section for details) and use the following F<evwrap.h> header file instead |
5021 | section for details) and use the following F<evwrap.h> header file instead |
3772 | of F<ev.h>: |
5022 | of F<ev.h>: |
3773 | |
5023 | |
… | |
… | |
3780 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
5030 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3781 | |
5031 | |
3782 | #include "evwrap.h" |
5032 | #include "evwrap.h" |
3783 | #include "ev.c" |
5033 | #include "ev.c" |
3784 | |
5034 | |
3785 | =over 4 |
|
|
3786 | |
|
|
3787 | =item The winsocket select function |
5035 | =head3 The winsocket C<select> function |
3788 | |
5036 | |
3789 | The winsocket C<select> function doesn't follow POSIX in that it |
5037 | The winsocket C<select> function doesn't follow POSIX in that it |
3790 | requires socket I<handles> and not socket I<file descriptors> (it is |
5038 | requires socket I<handles> and not socket I<file descriptors> (it is |
3791 | also extremely buggy). This makes select very inefficient, and also |
5039 | also extremely buggy). This makes select very inefficient, and also |
3792 | requires a mapping from file descriptors to socket handles (the Microsoft |
5040 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3801 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5049 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3802 | |
5050 | |
3803 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5051 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3804 | complexity in the O(n²) range when using win32. |
5052 | complexity in the O(n²) range when using win32. |
3805 | |
5053 | |
3806 | =item Limited number of file descriptors |
5054 | =head3 Limited number of file descriptors |
3807 | |
5055 | |
3808 | Windows has numerous arbitrary (and low) limits on things. |
5056 | Windows has numerous arbitrary (and low) limits on things. |
3809 | |
5057 | |
3810 | Early versions of winsocket's select only supported waiting for a maximum |
5058 | Early versions of winsocket's select only supported waiting for a maximum |
3811 | of C<64> handles (probably owning to the fact that all windows kernels |
5059 | of C<64> handles (probably owning to the fact that all windows kernels |
3812 | can only wait for C<64> things at the same time internally; Microsoft |
5060 | can only wait for C<64> things at the same time internally; Microsoft |
3813 | recommends spawning a chain of threads and wait for 63 handles and the |
5061 | recommends spawning a chain of threads and wait for 63 handles and the |
3814 | previous thread in each. Great). |
5062 | previous thread in each. Sounds great!). |
3815 | |
5063 | |
3816 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
5064 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3817 | to some high number (e.g. C<2048>) before compiling the winsocket select |
5065 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3818 | call (which might be in libev or elsewhere, for example, perl does its own |
5066 | call (which might be in libev or elsewhere, for example, perl and many |
3819 | select emulation on windows). |
5067 | other interpreters do their own select emulation on windows). |
3820 | |
5068 | |
3821 | Another limit is the number of file descriptors in the Microsoft runtime |
5069 | Another limit is the number of file descriptors in the Microsoft runtime |
3822 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
5070 | libraries, which by default is C<64> (there must be a hidden I<64> |
3823 | or something like this inside Microsoft). You can increase this by calling |
5071 | fetish or something like this inside Microsoft). You can increase this |
3824 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
5072 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3825 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
5073 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3826 | libraries. |
|
|
3827 | |
|
|
3828 | This might get you to about C<512> or C<2048> sockets (depending on |
5074 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3829 | windows version and/or the phase of the moon). To get more, you need to |
5075 | (depending on windows version and/or the phase of the moon). To get more, |
3830 | wrap all I/O functions and provide your own fd management, but the cost of |
5076 | you need to wrap all I/O functions and provide your own fd management, but |
3831 | calling select (O(n²)) will likely make this unworkable. |
5077 | the cost of calling select (O(n²)) will likely make this unworkable. |
3832 | |
|
|
3833 | =back |
|
|
3834 | |
5078 | |
3835 | =head2 PORTABILITY REQUIREMENTS |
5079 | =head2 PORTABILITY REQUIREMENTS |
3836 | |
5080 | |
3837 | In addition to a working ISO-C implementation and of course the |
5081 | In addition to a working ISO-C implementation and of course the |
3838 | backend-specific APIs, libev relies on a few additional extensions: |
5082 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
3845 | Libev assumes not only that all watcher pointers have the same internal |
5089 | Libev assumes not only that all watcher pointers have the same internal |
3846 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5090 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
3847 | assumes that the same (machine) code can be used to call any watcher |
5091 | assumes that the same (machine) code can be used to call any watcher |
3848 | callback: The watcher callbacks have different type signatures, but libev |
5092 | callback: The watcher callbacks have different type signatures, but libev |
3849 | calls them using an C<ev_watcher *> internally. |
5093 | calls them using an C<ev_watcher *> internally. |
|
|
5094 | |
|
|
5095 | =item pointer accesses must be thread-atomic |
|
|
5096 | |
|
|
5097 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5098 | writable in one piece - this is the case on all current architectures. |
3850 | |
5099 | |
3851 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5100 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3852 | |
5101 | |
3853 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5102 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3854 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5103 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
3877 | watchers. |
5126 | watchers. |
3878 | |
5127 | |
3879 | =item C<double> must hold a time value in seconds with enough accuracy |
5128 | =item C<double> must hold a time value in seconds with enough accuracy |
3880 | |
5129 | |
3881 | The type C<double> is used to represent timestamps. It is required to |
5130 | The type C<double> is used to represent timestamps. It is required to |
3882 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5131 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3883 | enough for at least into the year 4000. This requirement is fulfilled by |
5132 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5133 | (the design goal for libev). This requirement is overfulfilled by |
3884 | implementations implementing IEEE 754 (basically all existing ones). |
5134 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5135 | |
|
|
5136 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5137 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5138 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5139 | something like that, just kidding). |
3885 | |
5140 | |
3886 | =back |
5141 | =back |
3887 | |
5142 | |
3888 | If you know of other additional requirements drop me a note. |
5143 | If you know of other additional requirements drop me a note. |
3889 | |
5144 | |
… | |
… | |
3951 | =item Processing ev_async_send: O(number_of_async_watchers) |
5206 | =item Processing ev_async_send: O(number_of_async_watchers) |
3952 | |
5207 | |
3953 | =item Processing signals: O(max_signal_number) |
5208 | =item Processing signals: O(max_signal_number) |
3954 | |
5209 | |
3955 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5210 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
3956 | calls in the current loop iteration. Checking for async and signal events |
5211 | calls in the current loop iteration and the loop is currently |
|
|
5212 | blocked. Checking for async and signal events involves iterating over all |
3957 | involves iterating over all running async watchers or all signal numbers. |
5213 | running async watchers or all signal numbers. |
3958 | |
5214 | |
3959 | =back |
5215 | =back |
3960 | |
5216 | |
3961 | |
5217 | |
|
|
5218 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5219 | |
|
|
5220 | The major version 4 introduced some incompatible changes to the API. |
|
|
5221 | |
|
|
5222 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5223 | for all changes, so most programs should still compile. The compatibility |
|
|
5224 | layer might be removed in later versions of libev, so better update to the |
|
|
5225 | new API early than late. |
|
|
5226 | |
|
|
5227 | =over 4 |
|
|
5228 | |
|
|
5229 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5230 | |
|
|
5231 | The backward compatibility mechanism can be controlled by |
|
|
5232 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5233 | section. |
|
|
5234 | |
|
|
5235 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5236 | |
|
|
5237 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5238 | |
|
|
5239 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5240 | ev_loop_fork (EV_DEFAULT); |
|
|
5241 | |
|
|
5242 | =item function/symbol renames |
|
|
5243 | |
|
|
5244 | A number of functions and symbols have been renamed: |
|
|
5245 | |
|
|
5246 | ev_loop => ev_run |
|
|
5247 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5248 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5249 | |
|
|
5250 | ev_unloop => ev_break |
|
|
5251 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5252 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5253 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5254 | |
|
|
5255 | EV_TIMEOUT => EV_TIMER |
|
|
5256 | |
|
|
5257 | ev_loop_count => ev_iteration |
|
|
5258 | ev_loop_depth => ev_depth |
|
|
5259 | ev_loop_verify => ev_verify |
|
|
5260 | |
|
|
5261 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5262 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5263 | associated constants have been renamed to not collide with the C<struct |
|
|
5264 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5265 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5266 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5267 | typedef. |
|
|
5268 | |
|
|
5269 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5270 | |
|
|
5271 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5272 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5273 | and work, but the library code will of course be larger. |
|
|
5274 | |
|
|
5275 | =back |
|
|
5276 | |
|
|
5277 | |
|
|
5278 | =head1 GLOSSARY |
|
|
5279 | |
|
|
5280 | =over 4 |
|
|
5281 | |
|
|
5282 | =item active |
|
|
5283 | |
|
|
5284 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5285 | See L<WATCHER STATES> for details. |
|
|
5286 | |
|
|
5287 | =item application |
|
|
5288 | |
|
|
5289 | In this document, an application is whatever is using libev. |
|
|
5290 | |
|
|
5291 | =item backend |
|
|
5292 | |
|
|
5293 | The part of the code dealing with the operating system interfaces. |
|
|
5294 | |
|
|
5295 | =item callback |
|
|
5296 | |
|
|
5297 | The address of a function that is called when some event has been |
|
|
5298 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5299 | received the event, and the actual event bitset. |
|
|
5300 | |
|
|
5301 | =item callback/watcher invocation |
|
|
5302 | |
|
|
5303 | The act of calling the callback associated with a watcher. |
|
|
5304 | |
|
|
5305 | =item event |
|
|
5306 | |
|
|
5307 | A change of state of some external event, such as data now being available |
|
|
5308 | for reading on a file descriptor, time having passed or simply not having |
|
|
5309 | any other events happening anymore. |
|
|
5310 | |
|
|
5311 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5312 | C<EV_TIMER>). |
|
|
5313 | |
|
|
5314 | =item event library |
|
|
5315 | |
|
|
5316 | A software package implementing an event model and loop. |
|
|
5317 | |
|
|
5318 | =item event loop |
|
|
5319 | |
|
|
5320 | An entity that handles and processes external events and converts them |
|
|
5321 | into callback invocations. |
|
|
5322 | |
|
|
5323 | =item event model |
|
|
5324 | |
|
|
5325 | The model used to describe how an event loop handles and processes |
|
|
5326 | watchers and events. |
|
|
5327 | |
|
|
5328 | =item pending |
|
|
5329 | |
|
|
5330 | A watcher is pending as soon as the corresponding event has been |
|
|
5331 | detected. See L<WATCHER STATES> for details. |
|
|
5332 | |
|
|
5333 | =item real time |
|
|
5334 | |
|
|
5335 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5336 | |
|
|
5337 | =item wall-clock time |
|
|
5338 | |
|
|
5339 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5340 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5341 | clock. |
|
|
5342 | |
|
|
5343 | =item watcher |
|
|
5344 | |
|
|
5345 | A data structure that describes interest in certain events. Watchers need |
|
|
5346 | to be started (attached to an event loop) before they can receive events. |
|
|
5347 | |
|
|
5348 | =back |
|
|
5349 | |
3962 | =head1 AUTHOR |
5350 | =head1 AUTHOR |
3963 | |
5351 | |
3964 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5352 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5353 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
3965 | |
5354 | |