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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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26 | puts ("stdin ready"); |
28 | puts ("stdin ready"); |
27 | // for one-shot events, one must manually stop the watcher |
29 | // for one-shot events, one must manually stop the watcher |
28 | // with its corresponding stop function. |
30 | // with its corresponding stop function. |
29 | ev_io_stop (EV_A_ w); |
31 | ev_io_stop (EV_A_ w); |
30 | |
32 | |
31 | // this causes all nested ev_loop's to stop iterating |
33 | // this causes all nested ev_run's to stop iterating |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
34 | ev_break (EV_A_ EVBREAK_ALL); |
33 | } |
35 | } |
34 | |
36 | |
35 | // another callback, this time for a time-out |
37 | // another callback, this time for a time-out |
36 | static void |
38 | static void |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
39 | timeout_cb (EV_P_ ev_timer *w, int revents) |
38 | { |
40 | { |
39 | puts ("timeout"); |
41 | puts ("timeout"); |
40 | // this causes the innermost ev_loop to stop iterating |
42 | // this causes the innermost ev_run to stop iterating |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
43 | ev_break (EV_A_ EVBREAK_ONE); |
42 | } |
44 | } |
43 | |
45 | |
44 | int |
46 | int |
45 | main (void) |
47 | main (void) |
46 | { |
48 | { |
47 | // use the default event loop unless you have special needs |
49 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
50 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
51 | |
50 | // initialise an io watcher, then start it |
52 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
53 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
54 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
55 | ev_io_start (loop, &stdin_watcher); |
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56 | // simple non-repeating 5.5 second timeout |
58 | // simple non-repeating 5.5 second timeout |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
59 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
58 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
59 | |
61 | |
60 | // now wait for events to arrive |
62 | // now wait for events to arrive |
61 | ev_loop (loop, 0); |
63 | ev_run (loop, 0); |
62 | |
64 | |
63 | // unloop was called, so exit |
65 | // break was called, so exit |
64 | return 0; |
66 | return 0; |
65 | } |
67 | } |
66 | |
68 | |
67 | =head1 ABOUT THIS DOCUMENT |
69 | =head1 ABOUT THIS DOCUMENT |
68 | |
70 | |
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75 | While this document tries to be as complete as possible in documenting |
77 | While this document tries to be as complete as possible in documenting |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
78 | libev, its usage and the rationale behind its design, it is not a tutorial |
77 | on event-based programming, nor will it introduce event-based programming |
79 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
80 | with libev. |
79 | |
81 | |
80 | Familarity with event based programming techniques in general is assumed |
82 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
83 | throughout this document. |
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84 | |
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85 | =head1 WHAT TO READ WHEN IN A HURRY |
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86 | |
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87 | This manual tries to be very detailed, but unfortunately, this also makes |
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88 | it very long. If you just want to know the basics of libev, I suggest |
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89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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91 | C<ev_timer> sections in L</WATCHER TYPES>. |
82 | |
92 | |
83 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
84 | |
94 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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95 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
96 | watcher. |
106 | watcher. |
97 | |
107 | |
98 | =head2 FEATURES |
108 | =head2 FEATURES |
99 | |
109 | |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
114 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
107 | change events (C<ev_child>), and event watchers dealing with the event |
117 | change events (C<ev_child>), and event watchers dealing with the event |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
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124 | this argument. |
134 | this argument. |
125 | |
135 | |
126 | =head2 TIME REPRESENTATION |
136 | =head2 TIME REPRESENTATION |
127 | |
137 | |
128 | Libev represents time as a single floating point number, representing |
138 | Libev represents time as a single floating point number, representing |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
139 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
130 | near the beginning of 1970, details are complicated, don't ask). This |
140 | somewhere near the beginning of 1970, details are complicated, don't |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
141 | ask). This type is called C<ev_tstamp>, which is what you should use |
132 | aliases to the C<double> type in C. When you need to do any calculations |
142 | too. It usually aliases to the C<double> type in C. When you need to do |
133 | on it, you should treat it as some floating point value. Unlike the name |
143 | any calculations on it, you should treat it as some floating point value. |
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144 | |
134 | component C<stamp> might indicate, it is also used for time differences |
145 | Unlike the name component C<stamp> might indicate, it is also used for |
135 | throughout libev. |
146 | time differences (e.g. delays) throughout libev. |
136 | |
147 | |
137 | =head1 ERROR HANDLING |
148 | =head1 ERROR HANDLING |
138 | |
149 | |
139 | Libev knows three classes of errors: operating system errors, usage errors |
150 | Libev knows three classes of errors: operating system errors, usage errors |
140 | and internal errors (bugs). |
151 | and internal errors (bugs). |
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148 | When libev detects a usage error such as a negative timer interval, then |
159 | When libev detects a usage error such as a negative timer interval, then |
149 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
150 | so C<NDEBUG> will disable this checking): these are programming errors in |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
151 | the libev caller and need to be fixed there. |
162 | the libev caller and need to be fixed there. |
152 | |
163 | |
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164 | Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive |
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165 | consistency checking code inside libev that can be used to check for |
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166 | internal inconsistencies, suually caused by application bugs. |
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167 | |
153 | Libev also has a few internal error-checking C<assert>ions, and also has |
168 | Libev also has a few internal error-checking C<assert>ions. These do not |
154 | extensive consistency checking code. These do not trigger under normal |
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155 | circumstances, as they indicate either a bug in libev or worse. |
169 | trigger under normal circumstances, as they indicate either a bug in libev |
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170 | or worse. |
156 | |
171 | |
157 | |
172 | |
158 | =head1 GLOBAL FUNCTIONS |
173 | =head1 GLOBAL FUNCTIONS |
159 | |
174 | |
160 | These functions can be called anytime, even before initialising the |
175 | These functions can be called anytime, even before initialising the |
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164 | |
179 | |
165 | =item ev_tstamp ev_time () |
180 | =item ev_tstamp ev_time () |
166 | |
181 | |
167 | Returns the current time as libev would use it. Please note that the |
182 | Returns the current time as libev would use it. Please note that the |
168 | C<ev_now> function is usually faster and also often returns the timestamp |
183 | C<ev_now> function is usually faster and also often returns the timestamp |
169 | you actually want to know. |
184 | you actually want to know. Also interesting is the combination of |
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185 | C<ev_now_update> and C<ev_now>. |
170 | |
186 | |
171 | =item ev_sleep (ev_tstamp interval) |
187 | =item ev_sleep (ev_tstamp interval) |
172 | |
188 | |
173 | Sleep for the given interval: The current thread will be blocked until |
189 | Sleep for the given interval: The current thread will be blocked |
174 | either it is interrupted or the given time interval has passed. Basically |
190 | until either it is interrupted or the given time interval has |
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191 | passed (approximately - it might return a bit earlier even if not |
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192 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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193 | |
175 | this is a sub-second-resolution C<sleep ()>. |
194 | Basically this is a sub-second-resolution C<sleep ()>. |
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195 | |
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196 | The range of the C<interval> is limited - libev only guarantees to work |
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197 | with sleep times of up to one day (C<< interval <= 86400 >>). |
176 | |
198 | |
177 | =item int ev_version_major () |
199 | =item int ev_version_major () |
178 | |
200 | |
179 | =item int ev_version_minor () |
201 | =item int ev_version_minor () |
180 | |
202 | |
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191 | as this indicates an incompatible change. Minor versions are usually |
213 | as this indicates an incompatible change. Minor versions are usually |
192 | compatible to older versions, so a larger minor version alone is usually |
214 | compatible to older versions, so a larger minor version alone is usually |
193 | not a problem. |
215 | not a problem. |
194 | |
216 | |
195 | Example: Make sure we haven't accidentally been linked against the wrong |
217 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | version. |
218 | version (note, however, that this will not detect other ABI mismatches, |
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219 | such as LFS or reentrancy). |
197 | |
220 | |
198 | assert (("libev version mismatch", |
221 | assert (("libev version mismatch", |
199 | ev_version_major () == EV_VERSION_MAJOR |
222 | ev_version_major () == EV_VERSION_MAJOR |
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
223 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | |
224 | |
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212 | assert (("sorry, no epoll, no sex", |
235 | assert (("sorry, no epoll, no sex", |
213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
236 | ev_supported_backends () & EVBACKEND_EPOLL)); |
214 | |
237 | |
215 | =item unsigned int ev_recommended_backends () |
238 | =item unsigned int ev_recommended_backends () |
216 | |
239 | |
217 | Return the set of all backends compiled into this binary of libev and also |
240 | Return the set of all backends compiled into this binary of libev and |
218 | recommended for this platform. This set is often smaller than the one |
241 | also recommended for this platform, meaning it will work for most file |
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242 | descriptor types. This set is often smaller than the one returned by |
219 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
243 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
220 | most BSDs and will not be auto-detected unless you explicitly request it |
244 | and will not be auto-detected unless you explicitly request it (assuming |
221 | (assuming you know what you are doing). This is the set of backends that |
245 | you know what you are doing). This is the set of backends that libev will |
222 | libev will probe for if you specify no backends explicitly. |
246 | probe for if you specify no backends explicitly. |
223 | |
247 | |
224 | =item unsigned int ev_embeddable_backends () |
248 | =item unsigned int ev_embeddable_backends () |
225 | |
249 | |
226 | Returns the set of backends that are embeddable in other event loops. This |
250 | Returns the set of backends that are embeddable in other event loops. This |
227 | is the theoretical, all-platform, value. To find which backends |
251 | value is platform-specific but can include backends not available on the |
228 | might be supported on the current system, you would need to look at |
252 | current system. To find which embeddable backends might be supported on |
229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
253 | the current system, you would need to look at C<ev_embeddable_backends () |
230 | recommended ones. |
254 | & ev_supported_backends ()>, likewise for recommended ones. |
231 | |
255 | |
232 | See the description of C<ev_embed> watchers for more info. |
256 | See the description of C<ev_embed> watchers for more info. |
233 | |
257 | |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
258 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
235 | |
259 | |
236 | Sets the allocation function to use (the prototype is similar - the |
260 | Sets the allocation function to use (the prototype is similar - the |
237 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
261 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
238 | used to allocate and free memory (no surprises here). If it returns zero |
262 | used to allocate and free memory (no surprises here). If it returns zero |
239 | when memory needs to be allocated (C<size != 0>), the library might abort |
263 | when memory needs to be allocated (C<size != 0>), the library might abort |
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245 | |
269 | |
246 | You could override this function in high-availability programs to, say, |
270 | You could override this function in high-availability programs to, say, |
247 | free some memory if it cannot allocate memory, to use a special allocator, |
271 | free some memory if it cannot allocate memory, to use a special allocator, |
248 | or even to sleep a while and retry until some memory is available. |
272 | or even to sleep a while and retry until some memory is available. |
249 | |
273 | |
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274 | Example: The following is the C<realloc> function that libev itself uses |
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275 | which should work with C<realloc> and C<free> functions of all kinds and |
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276 | is probably a good basis for your own implementation. |
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277 | |
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278 | static void * |
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279 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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280 | { |
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281 | if (size) |
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282 | return realloc (ptr, size); |
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283 | |
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284 | free (ptr); |
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285 | return 0; |
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286 | } |
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287 | |
250 | Example: Replace the libev allocator with one that waits a bit and then |
288 | Example: Replace the libev allocator with one that waits a bit and then |
251 | retries (example requires a standards-compliant C<realloc>). |
289 | retries. |
252 | |
290 | |
253 | static void * |
291 | static void * |
254 | persistent_realloc (void *ptr, size_t size) |
292 | persistent_realloc (void *ptr, size_t size) |
255 | { |
293 | { |
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294 | if (!size) |
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295 | { |
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296 | free (ptr); |
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297 | return 0; |
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298 | } |
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299 | |
256 | for (;;) |
300 | for (;;) |
257 | { |
301 | { |
258 | void *newptr = realloc (ptr, size); |
302 | void *newptr = realloc (ptr, size); |
259 | |
303 | |
260 | if (newptr) |
304 | if (newptr) |
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265 | } |
309 | } |
266 | |
310 | |
267 | ... |
311 | ... |
268 | ev_set_allocator (persistent_realloc); |
312 | ev_set_allocator (persistent_realloc); |
269 | |
313 | |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
314 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
271 | |
315 | |
272 | Set the callback function to call on a retryable system call error (such |
316 | Set the callback function to call on a retryable system call error (such |
273 | as failed select, poll, epoll_wait). The message is a printable string |
317 | as failed select, poll, epoll_wait). The message is a printable string |
274 | indicating the system call or subsystem causing the problem. If this |
318 | indicating the system call or subsystem causing the problem. If this |
275 | callback is set, then libev will expect it to remedy the situation, no |
319 | callback is set, then libev will expect it to remedy the situation, no |
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287 | } |
331 | } |
288 | |
332 | |
289 | ... |
333 | ... |
290 | ev_set_syserr_cb (fatal_error); |
334 | ev_set_syserr_cb (fatal_error); |
291 | |
335 | |
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336 | =item ev_feed_signal (int signum) |
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337 | |
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338 | This function can be used to "simulate" a signal receive. It is completely |
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339 | safe to call this function at any time, from any context, including signal |
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340 | handlers or random threads. |
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341 | |
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342 | Its main use is to customise signal handling in your process, especially |
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343 | in the presence of threads. For example, you could block signals |
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344 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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345 | creating any loops), and in one thread, use C<sigwait> or any other |
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346 | mechanism to wait for signals, then "deliver" them to libev by calling |
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347 | C<ev_feed_signal>. |
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348 | |
292 | =back |
349 | =back |
293 | |
350 | |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
351 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
295 | |
352 | |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
353 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
297 | is I<not> optional in this case, as there is also an C<ev_loop> |
354 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
298 | I<function>). |
355 | libev 3 had an C<ev_loop> function colliding with the struct name). |
299 | |
356 | |
300 | The library knows two types of such loops, the I<default> loop, which |
357 | The library knows two types of such loops, the I<default> loop, which |
301 | supports signals and child events, and dynamically created loops which do |
358 | supports child process events, and dynamically created event loops which |
302 | not. |
359 | do not. |
303 | |
360 | |
304 | =over 4 |
361 | =over 4 |
305 | |
362 | |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
363 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
307 | |
364 | |
308 | This will initialise the default event loop if it hasn't been initialised |
365 | This returns the "default" event loop object, which is what you should |
309 | yet and return it. If the default loop could not be initialised, returns |
366 | normally use when you just need "the event loop". Event loop objects and |
310 | false. If it already was initialised it simply returns it (and ignores the |
367 | the C<flags> parameter are described in more detail in the entry for |
311 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
368 | C<ev_loop_new>. |
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369 | |
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370 | If the default loop is already initialised then this function simply |
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371 | returns it (and ignores the flags. If that is troubling you, check |
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372 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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373 | flags, which should almost always be C<0>, unless the caller is also the |
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374 | one calling C<ev_run> or otherwise qualifies as "the main program". |
312 | |
375 | |
313 | If you don't know what event loop to use, use the one returned from this |
376 | If you don't know what event loop to use, use the one returned from this |
314 | function. |
377 | function (or via the C<EV_DEFAULT> macro). |
315 | |
378 | |
316 | Note that this function is I<not> thread-safe, so if you want to use it |
379 | Note that this function is I<not> thread-safe, so if you want to use it |
317 | from multiple threads, you have to lock (note also that this is unlikely, |
380 | from multiple threads, you have to employ some kind of mutex (note also |
318 | as loops cannot be shared easily between threads anyway). |
381 | that this case is unlikely, as loops cannot be shared easily between |
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382 | threads anyway). |
319 | |
383 | |
320 | The default loop is the only loop that can handle C<ev_signal> and |
384 | The default loop is the only loop that can handle C<ev_child> watchers, |
321 | C<ev_child> watchers, and to do this, it always registers a handler |
385 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
322 | for C<SIGCHLD>. If this is a problem for your application you can either |
386 | a problem for your application you can either create a dynamic loop with |
323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
387 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
324 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
388 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
325 | C<ev_default_init>. |
389 | |
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390 | Example: This is the most typical usage. |
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391 | |
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392 | if (!ev_default_loop (0)) |
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393 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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394 | |
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395 | Example: Restrict libev to the select and poll backends, and do not allow |
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396 | environment settings to be taken into account: |
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397 | |
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398 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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399 | |
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400 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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401 | |
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402 | This will create and initialise a new event loop object. If the loop |
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403 | could not be initialised, returns false. |
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404 | |
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405 | This function is thread-safe, and one common way to use libev with |
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406 | threads is indeed to create one loop per thread, and using the default |
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407 | loop in the "main" or "initial" thread. |
326 | |
408 | |
327 | The flags argument can be used to specify special behaviour or specific |
409 | The flags argument can be used to specify special behaviour or specific |
328 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
410 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
329 | |
411 | |
330 | The following flags are supported: |
412 | The following flags are supported: |
… | |
… | |
340 | |
422 | |
341 | If this flag bit is or'ed into the flag value (or the program runs setuid |
423 | If this flag bit is or'ed into the flag value (or the program runs setuid |
342 | or setgid) then libev will I<not> look at the environment variable |
424 | or setgid) then libev will I<not> look at the environment variable |
343 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
425 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
344 | override the flags completely if it is found in the environment. This is |
426 | override the flags completely if it is found in the environment. This is |
345 | useful to try out specific backends to test their performance, or to work |
427 | useful to try out specific backends to test their performance, to work |
346 | around bugs. |
428 | around bugs, or to make libev threadsafe (accessing environment variables |
|
|
429 | cannot be done in a threadsafe way, but usually it works if no other |
|
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430 | thread modifies them). |
347 | |
431 | |
348 | =item C<EVFLAG_FORKCHECK> |
432 | =item C<EVFLAG_FORKCHECK> |
349 | |
433 | |
350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
434 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
351 | a fork, you can also make libev check for a fork in each iteration by |
435 | make libev check for a fork in each iteration by enabling this flag. |
352 | enabling this flag. |
|
|
353 | |
436 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
437 | This works by calling C<getpid ()> on every iteration of the loop, |
355 | and thus this might slow down your event loop if you do a lot of loop |
438 | and thus this might slow down your event loop if you do a lot of loop |
356 | iterations and little real work, but is usually not noticeable (on my |
439 | iterations and little real work, but is usually not noticeable (on my |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
440 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
358 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
441 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
359 | C<pthread_atfork> which is even faster). |
442 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
443 | versions 2.25 apparently removed the C<getpid> optimisation again). |
360 | |
444 | |
361 | The big advantage of this flag is that you can forget about fork (and |
445 | The big advantage of this flag is that you can forget about fork (and |
362 | forget about forgetting to tell libev about forking) when you use this |
446 | forget about forgetting to tell libev about forking, although you still |
363 | flag. |
447 | have to ignore C<SIGPIPE>) when you use this flag. |
364 | |
448 | |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
449 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
366 | environment variable. |
450 | environment variable. |
367 | |
451 | |
368 | =item C<EVFLAG_NOINOTIFY> |
452 | =item C<EVFLAG_NOINOTIFY> |
369 | |
453 | |
370 | When this flag is specified, then libev will not attempt to use the |
454 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
455 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
456 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
457 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
458 | |
375 | =item C<EVFLAG_SIGNALFD> |
459 | =item C<EVFLAG_SIGNALFD> |
376 | |
460 | |
377 | When this flag is specified, then libev will attempt to use the |
461 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
462 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
379 | delivers signals synchronously, which makes it both faster and might make |
463 | delivers signals synchronously, which makes it both faster and might make |
380 | it possible to get the queued signal data. It can also simplify signal |
464 | it possible to get the queued signal data. It can also simplify signal |
381 | handling with threads, as long as you properly block signals in your |
465 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
466 | threads that are not interested in handling them. |
383 | |
467 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
468 | Signalfd will not be used by default as this changes your signal mask, and |
385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
469 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
470 | example) that can't properly initialise their signal masks. |
|
|
471 | |
|
|
472 | =item C<EVFLAG_NOSIGMASK> |
|
|
473 | |
|
|
474 | When this flag is specified, then libev will avoid to modify the signal |
|
|
475 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
476 | when you want to receive them. |
|
|
477 | |
|
|
478 | This behaviour is useful when you want to do your own signal handling, or |
|
|
479 | want to handle signals only in specific threads and want to avoid libev |
|
|
480 | unblocking the signals. |
|
|
481 | |
|
|
482 | It's also required by POSIX in a threaded program, as libev calls |
|
|
483 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
484 | |
|
|
485 | =item C<EVFLAG_NOTIMERFD> |
|
|
486 | |
|
|
487 | When this flag is specified, the libev will avoid using a C<timerfd> to |
|
|
488 | detect time jumps. It will still be able to detect time jumps, but takes |
|
|
489 | longer and has a lower accuracy in doing so, but saves a file descriptor |
|
|
490 | per loop. |
|
|
491 | |
|
|
492 | The current implementation only tries to use a C<timerfd> when the first |
|
|
493 | C<ev_periodic> watcher is started and falls back on other methods if it |
|
|
494 | cannot be created, but this behaviour might change in the future. |
387 | |
495 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
496 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
497 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
498 | This is your standard select(2) backend. Not I<completely> standard, as |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
499 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
524 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
525 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
418 | |
526 | |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
527 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
420 | |
528 | |
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
529 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
422 | kernels). |
530 | kernels). |
423 | |
531 | |
424 | For few fds, this backend is a bit little slower than poll and select, |
532 | For few fds, this backend is a bit little slower than poll and select, but |
425 | but it scales phenomenally better. While poll and select usually scale |
533 | it scales phenomenally better. While poll and select usually scale like |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
534 | O(total_fds) where total_fds is the total number of fds (or the highest |
427 | epoll scales either O(1) or O(active_fds). |
535 | fd), epoll scales either O(1) or O(active_fds). |
428 | |
536 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
537 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
538 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
539 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
540 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
541 | returning before the timeout value, resulting in additional iterations |
|
|
542 | (and only giving 5ms accuracy while select on the same platform gives |
433 | so on. The biggest issue is fork races, however - if a program forks then |
543 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
434 | I<both> parent and child process have to recreate the epoll set, which can |
544 | forks then I<both> parent and child process have to recreate the epoll |
435 | take considerable time (one syscall per file descriptor) and is of course |
545 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
546 | and is of course hard to detect. |
437 | |
547 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
548 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
549 | but of course I<doesn't>, and epoll just loves to report events for |
440 | I<different> file descriptors (even already closed ones, so one cannot |
550 | totally I<different> file descriptors (even already closed ones, so |
441 | even remove them from the set) than registered in the set (especially |
551 | one cannot even remove them from the set) than registered in the set |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
552 | (especially on SMP systems). Libev tries to counter these spurious |
443 | employing an additional generation counter and comparing that against the |
553 | notifications by employing an additional generation counter and comparing |
444 | events to filter out spurious ones, recreating the set when required. |
554 | that against the events to filter out spurious ones, recreating the set |
|
|
555 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
556 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
557 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
558 | not least, it also refuses to work with some file descriptors which work |
|
|
559 | perfectly fine with C<select> (files, many character devices...). |
|
|
560 | |
|
|
561 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
562 | cobbled together in a hurry, no thought to design or interaction with |
|
|
563 | others. Oh, the pain, will it ever stop... |
445 | |
564 | |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
565 | While stopping, setting and starting an I/O watcher in the same iteration |
447 | will result in some caching, there is still a system call per such |
566 | will result in some caching, there is still a system call per such |
448 | incident (because the same I<file descriptor> could point to a different |
567 | incident (because the same I<file descriptor> could point to a different |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
568 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
461 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
580 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
462 | faster than epoll for maybe up to a hundred file descriptors, depending on |
581 | faster than epoll for maybe up to a hundred file descriptors, depending on |
463 | the usage. So sad. |
582 | the usage. So sad. |
464 | |
583 | |
465 | While nominally embeddable in other event loops, this feature is broken in |
584 | While nominally embeddable in other event loops, this feature is broken in |
466 | all kernel versions tested so far. |
585 | a lot of kernel revisions, but probably(!) works in current versions. |
467 | |
586 | |
468 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
587 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
469 | C<EVBACKEND_POLL>. |
588 | C<EVBACKEND_POLL>. |
470 | |
589 | |
|
|
590 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
591 | |
|
|
592 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
|
|
593 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
|
|
594 | only tries to use it in 4.19+). |
|
|
595 | |
|
|
596 | This is another Linux train wreck of an event interface. |
|
|
597 | |
|
|
598 | If this backend works for you (as of this writing, it was very |
|
|
599 | experimental), it is the best event interface available on Linux and might |
|
|
600 | be well worth enabling it - if it isn't available in your kernel this will |
|
|
601 | be detected and this backend will be skipped. |
|
|
602 | |
|
|
603 | This backend can batch oneshot requests and supports a user-space ring |
|
|
604 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
605 | problems of epoll (such as not being able to remove event sources from |
|
|
606 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
607 | being the Linux kernel, of course it suffers from a whole new set of |
|
|
608 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
609 | issues. |
|
|
610 | |
|
|
611 | For one, it is not easily embeddable (but probably could be done using |
|
|
612 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
613 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
|
|
614 | requests are left, this backend will be skipped during initialisation, and |
|
|
615 | will switch to epoll when the loop is active. |
|
|
616 | |
|
|
617 | Most problematic in practice, however, is that not all file descriptors |
|
|
618 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
|
|
619 | files, F</dev/null> and many others are supported, but ttys do not work |
|
|
620 | properly (a known bug that the kernel developers don't care about, see |
|
|
621 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
622 | (yet?) a generic event polling interface. |
|
|
623 | |
|
|
624 | Overall, it seems the Linux developers just don't want it to have a |
|
|
625 | generic event handling mechanism other than C<select> or C<poll>. |
|
|
626 | |
|
|
627 | To work around all these problem, the current version of libev uses its |
|
|
628 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
629 | falls back completely to epoll if the kernel acts up. |
|
|
630 | |
|
|
631 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
632 | C<EVBACKEND_POLL>. |
|
|
633 | |
471 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
634 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
472 | |
635 | |
473 | Kqueue deserves special mention, as at the time of this writing, it |
636 | Kqueue deserves special mention, as at the time this backend was |
474 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
637 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
475 | with anything but sockets and pipes, except on Darwin, where of course |
638 | work reliably with anything but sockets and pipes, except on Darwin, |
476 | it's completely useless). Unlike epoll, however, whose brokenness |
639 | where of course it's completely useless). Unlike epoll, however, whose |
477 | is by design, these kqueue bugs can (and eventually will) be fixed |
640 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
478 | without API changes to existing programs. For this reason it's not being |
641 | fixed without API changes to existing programs. For this reason it's not |
479 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
642 | being "auto-detected" on all platforms unless you explicitly specify it |
480 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
643 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
481 | system like NetBSD. |
644 | known-to-be-good (-enough) system like NetBSD. |
482 | |
645 | |
483 | You still can embed kqueue into a normal poll or select backend and use it |
646 | You still can embed kqueue into a normal poll or select backend and use it |
484 | only for sockets (after having made sure that sockets work with kqueue on |
647 | only for sockets (after having made sure that sockets work with kqueue on |
485 | the target platform). See C<ev_embed> watchers for more info. |
648 | the target platform). See C<ev_embed> watchers for more info. |
486 | |
649 | |
487 | It scales in the same way as the epoll backend, but the interface to the |
650 | It scales in the same way as the epoll backend, but the interface to the |
488 | kernel is more efficient (which says nothing about its actual speed, of |
651 | kernel is more efficient (which says nothing about its actual speed, of |
489 | course). While stopping, setting and starting an I/O watcher does never |
652 | course). While stopping, setting and starting an I/O watcher does never |
490 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
653 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
491 | two event changes per incident. Support for C<fork ()> is very bad (but |
654 | two event changes per incident. Support for C<fork ()> is very bad (you |
492 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
655 | might have to leak fds on fork, but it's more sane than epoll) and it |
493 | cases |
656 | drops fds silently in similarly hard-to-detect cases. |
494 | |
657 | |
495 | This backend usually performs well under most conditions. |
658 | This backend usually performs well under most conditions. |
496 | |
659 | |
497 | While nominally embeddable in other event loops, this doesn't work |
660 | While nominally embeddable in other event loops, this doesn't work |
498 | everywhere, so you might need to test for this. And since it is broken |
661 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
515 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
678 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
516 | |
679 | |
517 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
680 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
518 | it's really slow, but it still scales very well (O(active_fds)). |
681 | it's really slow, but it still scales very well (O(active_fds)). |
519 | |
682 | |
520 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
521 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
522 | blocking when no data (or space) is available. |
|
|
523 | |
|
|
524 | While this backend scales well, it requires one system call per active |
683 | While this backend scales well, it requires one system call per active |
525 | file descriptor per loop iteration. For small and medium numbers of file |
684 | file descriptor per loop iteration. For small and medium numbers of file |
526 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
685 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
527 | might perform better. |
686 | might perform better. |
528 | |
687 | |
529 | On the positive side, with the exception of the spurious readiness |
688 | On the positive side, this backend actually performed fully to |
530 | notifications, this backend actually performed fully to specification |
|
|
531 | in all tests and is fully embeddable, which is a rare feat among the |
689 | specification in all tests and is fully embeddable, which is a rare feat |
532 | OS-specific backends (I vastly prefer correctness over speed hacks). |
690 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
691 | hacks). |
|
|
692 | |
|
|
693 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
694 | even sun itself gets it wrong in their code examples: The event polling |
|
|
695 | function sometimes returns events to the caller even though an error |
|
|
696 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
697 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
698 | absolutely have to know whether an event occurred or not because you have |
|
|
699 | to re-arm the watcher. |
|
|
700 | |
|
|
701 | Fortunately libev seems to be able to work around these idiocies. |
533 | |
702 | |
534 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
703 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
535 | C<EVBACKEND_POLL>. |
704 | C<EVBACKEND_POLL>. |
536 | |
705 | |
537 | =item C<EVBACKEND_ALL> |
706 | =item C<EVBACKEND_ALL> |
538 | |
707 | |
539 | Try all backends (even potentially broken ones that wouldn't be tried |
708 | Try all backends (even potentially broken ones that wouldn't be tried |
540 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
709 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
541 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
710 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
542 | |
711 | |
543 | It is definitely not recommended to use this flag. |
712 | It is definitely not recommended to use this flag, use whatever |
|
|
713 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
714 | at all. |
|
|
715 | |
|
|
716 | =item C<EVBACKEND_MASK> |
|
|
717 | |
|
|
718 | Not a backend at all, but a mask to select all backend bits from a |
|
|
719 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
720 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
544 | |
721 | |
545 | =back |
722 | =back |
546 | |
723 | |
547 | If one or more of the backend flags are or'ed into the flags value, |
724 | If one or more of the backend flags are or'ed into the flags value, |
548 | then only these backends will be tried (in the reverse order as listed |
725 | then only these backends will be tried (in the reverse order as listed |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
726 | here). If none are specified, all backends in C<ev_recommended_backends |
550 | ()> will be tried. |
727 | ()> will be tried. |
551 | |
728 | |
552 | Example: This is the most typical usage. |
|
|
553 | |
|
|
554 | if (!ev_default_loop (0)) |
|
|
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
556 | |
|
|
557 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
558 | environment settings to be taken into account: |
|
|
559 | |
|
|
560 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
561 | |
|
|
562 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
563 | used if available (warning, breaks stuff, best use only with your own |
|
|
564 | private event loop and only if you know the OS supports your types of |
|
|
565 | fds): |
|
|
566 | |
|
|
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
568 | |
|
|
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
570 | |
|
|
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
572 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
573 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
574 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
575 | |
|
|
576 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
577 | libev with threads is indeed to create one loop per thread, and using the |
|
|
578 | default loop in the "main" or "initial" thread. |
|
|
579 | |
|
|
580 | Example: Try to create a event loop that uses epoll and nothing else. |
729 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
730 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
731 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
732 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
733 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
734 | |
|
|
735 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
736 | used if available. |
|
|
737 | |
|
|
738 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
739 | |
|
|
740 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
741 | linux aio backend if possible, but fall back to something else if that |
|
|
742 | isn't available. |
|
|
743 | |
|
|
744 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
745 | |
586 | =item ev_default_destroy () |
746 | =item ev_loop_destroy (loop) |
587 | |
747 | |
588 | Destroys the default loop again (frees all memory and kernel state |
748 | Destroys an event loop object (frees all memory and kernel state |
589 | etc.). None of the active event watchers will be stopped in the normal |
749 | etc.). None of the active event watchers will be stopped in the normal |
590 | sense, so e.g. C<ev_is_active> might still return true. It is your |
750 | sense, so e.g. C<ev_is_active> might still return true. It is your |
591 | responsibility to either stop all watchers cleanly yourself I<before> |
751 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | calling this function, or cope with the fact afterwards (which is usually |
752 | calling this function, or cope with the fact afterwards (which is usually |
593 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
753 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
… | |
… | |
595 | |
755 | |
596 | Note that certain global state, such as signal state (and installed signal |
756 | Note that certain global state, such as signal state (and installed signal |
597 | handlers), will not be freed by this function, and related watchers (such |
757 | handlers), will not be freed by this function, and related watchers (such |
598 | as signal and child watchers) would need to be stopped manually. |
758 | as signal and child watchers) would need to be stopped manually. |
599 | |
759 | |
600 | In general it is not advisable to call this function except in the |
760 | This function is normally used on loop objects allocated by |
601 | rare occasion where you really need to free e.g. the signal handling |
761 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
762 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
763 | |
|
|
764 | Note that it is not advisable to call this function on the default loop |
|
|
765 | except in the rare occasion where you really need to free its resources. |
602 | pipe fds. If you need dynamically allocated loops it is better to use |
766 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
603 | C<ev_loop_new> and C<ev_loop_destroy>. |
767 | and C<ev_loop_destroy>. |
604 | |
768 | |
605 | =item ev_loop_destroy (loop) |
769 | =item ev_loop_fork (loop) |
606 | |
770 | |
607 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
608 | earlier call to C<ev_loop_new>. |
|
|
609 | |
|
|
610 | =item ev_default_fork () |
|
|
611 | |
|
|
612 | This function sets a flag that causes subsequent C<ev_loop> iterations |
771 | This function sets a flag that causes subsequent C<ev_run> iterations |
613 | to reinitialise the kernel state for backends that have one. Despite the |
772 | to reinitialise the kernel state for backends that have one. Despite |
614 | name, you can call it anytime, but it makes most sense after forking, in |
773 | the name, you can call it anytime you are allowed to start or stop |
615 | the child process (or both child and parent, but that again makes little |
774 | watchers (except inside an C<ev_prepare> callback), but it makes most |
616 | sense). You I<must> call it in the child before using any of the libev |
775 | sense after forking, in the child process. You I<must> call it (or use |
617 | functions, and it will only take effect at the next C<ev_loop> iteration. |
776 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
777 | |
|
|
778 | In addition, if you want to reuse a loop (via this function or |
|
|
779 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
780 | |
|
|
781 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
782 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
783 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
784 | during fork. |
618 | |
785 | |
619 | On the other hand, you only need to call this function in the child |
786 | On the other hand, you only need to call this function in the child |
620 | process if and only if you want to use the event library in the child. If |
787 | process if and only if you want to use the event loop in the child. If |
621 | you just fork+exec, you don't have to call it at all. |
788 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
789 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
790 | difference, but libev will usually detect this case on its own and do a |
|
|
791 | costly reset of the backend). |
622 | |
792 | |
623 | The function itself is quite fast and it's usually not a problem to call |
793 | The function itself is quite fast and it's usually not a problem to call |
624 | it just in case after a fork. To make this easy, the function will fit in |
794 | it just in case after a fork. |
625 | quite nicely into a call to C<pthread_atfork>: |
|
|
626 | |
795 | |
|
|
796 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
797 | using pthreads. |
|
|
798 | |
|
|
799 | static void |
|
|
800 | post_fork_child (void) |
|
|
801 | { |
|
|
802 | ev_loop_fork (EV_DEFAULT); |
|
|
803 | } |
|
|
804 | |
|
|
805 | ... |
627 | pthread_atfork (0, 0, ev_default_fork); |
806 | pthread_atfork (0, 0, post_fork_child); |
628 | |
|
|
629 | =item ev_loop_fork (loop) |
|
|
630 | |
|
|
631 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
632 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
633 | after fork that you want to re-use in the child, and how you do this is |
|
|
634 | entirely your own problem. |
|
|
635 | |
807 | |
636 | =item int ev_is_default_loop (loop) |
808 | =item int ev_is_default_loop (loop) |
637 | |
809 | |
638 | Returns true when the given loop is, in fact, the default loop, and false |
810 | Returns true when the given loop is, in fact, the default loop, and false |
639 | otherwise. |
811 | otherwise. |
640 | |
812 | |
641 | =item unsigned int ev_loop_count (loop) |
813 | =item unsigned int ev_iteration (loop) |
642 | |
814 | |
643 | Returns the count of loop iterations for the loop, which is identical to |
815 | Returns the current iteration count for the event loop, which is identical |
644 | the number of times libev did poll for new events. It starts at C<0> and |
816 | to the number of times libev did poll for new events. It starts at C<0> |
645 | happily wraps around with enough iterations. |
817 | and happily wraps around with enough iterations. |
646 | |
818 | |
647 | This value can sometimes be useful as a generation counter of sorts (it |
819 | This value can sometimes be useful as a generation counter of sorts (it |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
820 | "ticks" the number of loop iterations), as it roughly corresponds with |
649 | C<ev_prepare> and C<ev_check> calls. |
821 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
822 | prepare and check phases. |
650 | |
823 | |
651 | =item unsigned int ev_loop_depth (loop) |
824 | =item unsigned int ev_depth (loop) |
652 | |
825 | |
653 | Returns the number of times C<ev_loop> was entered minus the number of |
826 | Returns the number of times C<ev_run> was entered minus the number of |
654 | times C<ev_loop> was exited, in other words, the recursion depth. |
827 | times C<ev_run> was exited normally, in other words, the recursion depth. |
655 | |
828 | |
656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
829 | Outside C<ev_run>, this number is zero. In a callback, this number is |
657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
830 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
658 | in which case it is higher. |
831 | in which case it is higher. |
659 | |
832 | |
660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
833 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
661 | etc.), doesn't count as exit. |
834 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
835 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
836 | convenient, in which case it is fully supported. |
662 | |
837 | |
663 | =item unsigned int ev_backend (loop) |
838 | =item unsigned int ev_backend (loop) |
664 | |
839 | |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
840 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
666 | use. |
841 | use. |
… | |
… | |
675 | |
850 | |
676 | =item ev_now_update (loop) |
851 | =item ev_now_update (loop) |
677 | |
852 | |
678 | Establishes the current time by querying the kernel, updating the time |
853 | Establishes the current time by querying the kernel, updating the time |
679 | returned by C<ev_now ()> in the progress. This is a costly operation and |
854 | returned by C<ev_now ()> in the progress. This is a costly operation and |
680 | is usually done automatically within C<ev_loop ()>. |
855 | is usually done automatically within C<ev_run ()>. |
681 | |
856 | |
682 | This function is rarely useful, but when some event callback runs for a |
857 | This function is rarely useful, but when some event callback runs for a |
683 | very long time without entering the event loop, updating libev's idea of |
858 | very long time without entering the event loop, updating libev's idea of |
684 | the current time is a good idea. |
859 | the current time is a good idea. |
685 | |
860 | |
686 | See also L<The special problem of time updates> in the C<ev_timer> section. |
861 | See also L</The special problem of time updates> in the C<ev_timer> section. |
687 | |
862 | |
688 | =item ev_suspend (loop) |
863 | =item ev_suspend (loop) |
689 | |
864 | |
690 | =item ev_resume (loop) |
865 | =item ev_resume (loop) |
691 | |
866 | |
692 | These two functions suspend and resume a loop, for use when the loop is |
867 | These two functions suspend and resume an event loop, for use when the |
693 | not used for a while and timeouts should not be processed. |
868 | loop is not used for a while and timeouts should not be processed. |
694 | |
869 | |
695 | A typical use case would be an interactive program such as a game: When |
870 | A typical use case would be an interactive program such as a game: When |
696 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
871 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
697 | would be best to handle timeouts as if no time had actually passed while |
872 | would be best to handle timeouts as if no time had actually passed while |
698 | the program was suspended. This can be achieved by calling C<ev_suspend> |
873 | the program was suspended. This can be achieved by calling C<ev_suspend> |
… | |
… | |
700 | C<ev_resume> directly afterwards to resume timer processing. |
875 | C<ev_resume> directly afterwards to resume timer processing. |
701 | |
876 | |
702 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
877 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
703 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
878 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
704 | will be rescheduled (that is, they will lose any events that would have |
879 | will be rescheduled (that is, they will lose any events that would have |
705 | occured while suspended). |
880 | occurred while suspended). |
706 | |
881 | |
707 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
882 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
708 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
883 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
709 | without a previous call to C<ev_suspend>. |
884 | without a previous call to C<ev_suspend>. |
710 | |
885 | |
711 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
886 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
712 | event loop time (see C<ev_now_update>). |
887 | event loop time (see C<ev_now_update>). |
713 | |
888 | |
714 | =item ev_loop (loop, int flags) |
889 | =item bool ev_run (loop, int flags) |
715 | |
890 | |
716 | Finally, this is it, the event handler. This function usually is called |
891 | Finally, this is it, the event handler. This function usually is called |
717 | after you have initialised all your watchers and you want to start |
892 | after you have initialised all your watchers and you want to start |
718 | handling events. |
893 | handling events. It will ask the operating system for any new events, call |
|
|
894 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
895 | is why event loops are called I<loops>. |
719 | |
896 | |
720 | If the flags argument is specified as C<0>, it will not return until |
897 | If the flags argument is specified as C<0>, it will keep handling events |
721 | either no event watchers are active anymore or C<ev_unloop> was called. |
898 | until either no event watchers are active anymore or C<ev_break> was |
|
|
899 | called. |
722 | |
900 | |
|
|
901 | The return value is false if there are no more active watchers (which |
|
|
902 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
903 | (which usually means " you should call C<ev_run> again"). |
|
|
904 | |
723 | Please note that an explicit C<ev_unloop> is usually better than |
905 | Please note that an explicit C<ev_break> is usually better than |
724 | relying on all watchers to be stopped when deciding when a program has |
906 | relying on all watchers to be stopped when deciding when a program has |
725 | finished (especially in interactive programs), but having a program |
907 | finished (especially in interactive programs), but having a program |
726 | that automatically loops as long as it has to and no longer by virtue |
908 | that automatically loops as long as it has to and no longer by virtue |
727 | of relying on its watchers stopping correctly, that is truly a thing of |
909 | of relying on its watchers stopping correctly, that is truly a thing of |
728 | beauty. |
910 | beauty. |
729 | |
911 | |
|
|
912 | This function is I<mostly> exception-safe - you can break out of a |
|
|
913 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
914 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
915 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
916 | |
730 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
917 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
731 | those events and any already outstanding ones, but will not block your |
918 | those events and any already outstanding ones, but will not wait and |
732 | process in case there are no events and will return after one iteration of |
919 | block your process in case there are no events and will return after one |
733 | the loop. |
920 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
921 | events while doing lengthy calculations, to keep the program responsive. |
734 | |
922 | |
735 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
923 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
736 | necessary) and will handle those and any already outstanding ones. It |
924 | necessary) and will handle those and any already outstanding ones. It |
737 | will block your process until at least one new event arrives (which could |
925 | will block your process until at least one new event arrives (which could |
738 | be an event internal to libev itself, so there is no guarantee that a |
926 | be an event internal to libev itself, so there is no guarantee that a |
739 | user-registered callback will be called), and will return after one |
927 | user-registered callback will be called), and will return after one |
740 | iteration of the loop. |
928 | iteration of the loop. |
741 | |
929 | |
742 | This is useful if you are waiting for some external event in conjunction |
930 | This is useful if you are waiting for some external event in conjunction |
743 | with something not expressible using other libev watchers (i.e. "roll your |
931 | with something not expressible using other libev watchers (i.e. "roll your |
744 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
932 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
745 | usually a better approach for this kind of thing. |
933 | usually a better approach for this kind of thing. |
746 | |
934 | |
747 | Here are the gory details of what C<ev_loop> does: |
935 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
936 | understanding, not a guarantee that things will work exactly like this in |
|
|
937 | future versions): |
748 | |
938 | |
|
|
939 | - Increment loop depth. |
|
|
940 | - Reset the ev_break status. |
749 | - Before the first iteration, call any pending watchers. |
941 | - Before the first iteration, call any pending watchers. |
|
|
942 | LOOP: |
750 | * If EVFLAG_FORKCHECK was used, check for a fork. |
943 | - If EVFLAG_FORKCHECK was used, check for a fork. |
751 | - If a fork was detected (by any means), queue and call all fork watchers. |
944 | - If a fork was detected (by any means), queue and call all fork watchers. |
752 | - Queue and call all prepare watchers. |
945 | - Queue and call all prepare watchers. |
|
|
946 | - If ev_break was called, goto FINISH. |
753 | - If we have been forked, detach and recreate the kernel state |
947 | - If we have been forked, detach and recreate the kernel state |
754 | as to not disturb the other process. |
948 | as to not disturb the other process. |
755 | - Update the kernel state with all outstanding changes. |
949 | - Update the kernel state with all outstanding changes. |
756 | - Update the "event loop time" (ev_now ()). |
950 | - Update the "event loop time" (ev_now ()). |
757 | - Calculate for how long to sleep or block, if at all |
951 | - Calculate for how long to sleep or block, if at all |
758 | (active idle watchers, EVLOOP_NONBLOCK or not having |
952 | (active idle watchers, EVRUN_NOWAIT or not having |
759 | any active watchers at all will result in not sleeping). |
953 | any active watchers at all will result in not sleeping). |
760 | - Sleep if the I/O and timer collect interval say so. |
954 | - Sleep if the I/O and timer collect interval say so. |
|
|
955 | - Increment loop iteration counter. |
761 | - Block the process, waiting for any events. |
956 | - Block the process, waiting for any events. |
762 | - Queue all outstanding I/O (fd) events. |
957 | - Queue all outstanding I/O (fd) events. |
763 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
958 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
764 | - Queue all expired timers. |
959 | - Queue all expired timers. |
765 | - Queue all expired periodics. |
960 | - Queue all expired periodics. |
766 | - Unless any events are pending now, queue all idle watchers. |
961 | - Queue all idle watchers with priority higher than that of pending events. |
767 | - Queue all check watchers. |
962 | - Queue all check watchers. |
768 | - Call all queued watchers in reverse order (i.e. check watchers first). |
963 | - Call all queued watchers in reverse order (i.e. check watchers first). |
769 | Signals and child watchers are implemented as I/O watchers, and will |
964 | Signals and child watchers are implemented as I/O watchers, and will |
770 | be handled here by queueing them when their watcher gets executed. |
965 | be handled here by queueing them when their watcher gets executed. |
771 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
966 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
772 | were used, or there are no active watchers, return, otherwise |
967 | were used, or there are no active watchers, goto FINISH, otherwise |
773 | continue with step *. |
968 | continue with step LOOP. |
|
|
969 | FINISH: |
|
|
970 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
971 | - Decrement the loop depth. |
|
|
972 | - Return. |
774 | |
973 | |
775 | Example: Queue some jobs and then loop until no events are outstanding |
974 | Example: Queue some jobs and then loop until no events are outstanding |
776 | anymore. |
975 | anymore. |
777 | |
976 | |
778 | ... queue jobs here, make sure they register event watchers as long |
977 | ... queue jobs here, make sure they register event watchers as long |
779 | ... as they still have work to do (even an idle watcher will do..) |
978 | ... as they still have work to do (even an idle watcher will do..) |
780 | ev_loop (my_loop, 0); |
979 | ev_run (my_loop, 0); |
781 | ... jobs done or somebody called unloop. yeah! |
980 | ... jobs done or somebody called break. yeah! |
782 | |
981 | |
783 | =item ev_unloop (loop, how) |
982 | =item ev_break (loop, how) |
784 | |
983 | |
785 | Can be used to make a call to C<ev_loop> return early (but only after it |
984 | Can be used to make a call to C<ev_run> return early (but only after it |
786 | has processed all outstanding events). The C<how> argument must be either |
985 | has processed all outstanding events). The C<how> argument must be either |
787 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
986 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
788 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
987 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
789 | |
988 | |
790 | This "unloop state" will be cleared when entering C<ev_loop> again. |
989 | This "break state" will be cleared on the next call to C<ev_run>. |
791 | |
990 | |
792 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
991 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
992 | which case it will have no effect. |
793 | |
993 | |
794 | =item ev_ref (loop) |
994 | =item ev_ref (loop) |
795 | |
995 | |
796 | =item ev_unref (loop) |
996 | =item ev_unref (loop) |
797 | |
997 | |
798 | Ref/unref can be used to add or remove a reference count on the event |
998 | Ref/unref can be used to add or remove a reference count on the event |
799 | loop: Every watcher keeps one reference, and as long as the reference |
999 | loop: Every watcher keeps one reference, and as long as the reference |
800 | count is nonzero, C<ev_loop> will not return on its own. |
1000 | count is nonzero, C<ev_run> will not return on its own. |
801 | |
1001 | |
802 | This is useful when you have a watcher that you never intend to |
1002 | This is useful when you have a watcher that you never intend to |
803 | unregister, but that nevertheless should not keep C<ev_loop> from |
1003 | unregister, but that nevertheless should not keep C<ev_run> from |
804 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
1004 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
805 | before stopping it. |
1005 | before stopping it. |
806 | |
1006 | |
807 | As an example, libev itself uses this for its internal signal pipe: It |
1007 | As an example, libev itself uses this for its internal signal pipe: It |
808 | is not visible to the libev user and should not keep C<ev_loop> from |
1008 | is not visible to the libev user and should not keep C<ev_run> from |
809 | exiting if no event watchers registered by it are active. It is also an |
1009 | exiting if no event watchers registered by it are active. It is also an |
810 | excellent way to do this for generic recurring timers or from within |
1010 | excellent way to do this for generic recurring timers or from within |
811 | third-party libraries. Just remember to I<unref after start> and I<ref |
1011 | third-party libraries. Just remember to I<unref after start> and I<ref |
812 | before stop> (but only if the watcher wasn't active before, or was active |
1012 | before stop> (but only if the watcher wasn't active before, or was active |
813 | before, respectively. Note also that libev might stop watchers itself |
1013 | before, respectively. Note also that libev might stop watchers itself |
814 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
1014 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
815 | in the callback). |
1015 | in the callback). |
816 | |
1016 | |
817 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
1017 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
818 | running when nothing else is active. |
1018 | running when nothing else is active. |
819 | |
1019 | |
820 | ev_signal exitsig; |
1020 | ev_signal exitsig; |
821 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
1021 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
822 | ev_signal_start (loop, &exitsig); |
1022 | ev_signal_start (loop, &exitsig); |
823 | evf_unref (loop); |
1023 | ev_unref (loop); |
824 | |
1024 | |
825 | Example: For some weird reason, unregister the above signal handler again. |
1025 | Example: For some weird reason, unregister the above signal handler again. |
826 | |
1026 | |
827 | ev_ref (loop); |
1027 | ev_ref (loop); |
828 | ev_signal_stop (loop, &exitsig); |
1028 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
848 | overhead for the actual polling but can deliver many events at once. |
1048 | overhead for the actual polling but can deliver many events at once. |
849 | |
1049 | |
850 | By setting a higher I<io collect interval> you allow libev to spend more |
1050 | By setting a higher I<io collect interval> you allow libev to spend more |
851 | time collecting I/O events, so you can handle more events per iteration, |
1051 | time collecting I/O events, so you can handle more events per iteration, |
852 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1052 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
853 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1053 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
854 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
1054 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
855 | sleep time ensures that libev will not poll for I/O events more often then |
1055 | sleep time ensures that libev will not poll for I/O events more often then |
856 | once per this interval, on average. |
1056 | once per this interval, on average (as long as the host time resolution is |
|
|
1057 | good enough). |
857 | |
1058 | |
858 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1059 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
859 | to spend more time collecting timeouts, at the expense of increased |
1060 | to spend more time collecting timeouts, at the expense of increased |
860 | latency/jitter/inexactness (the watcher callback will be called |
1061 | latency/jitter/inexactness (the watcher callback will be called |
861 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
1062 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
1068 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
868 | as this approaches the timing granularity of most systems. Note that if |
1069 | as this approaches the timing granularity of most systems. Note that if |
869 | you do transactions with the outside world and you can't increase the |
1070 | you do transactions with the outside world and you can't increase the |
870 | parallelity, then this setting will limit your transaction rate (if you |
1071 | parallelity, then this setting will limit your transaction rate (if you |
871 | need to poll once per transaction and the I/O collect interval is 0.01, |
1072 | need to poll once per transaction and the I/O collect interval is 0.01, |
872 | then you can't do more than 100 transations per second). |
1073 | then you can't do more than 100 transactions per second). |
873 | |
1074 | |
874 | Setting the I<timeout collect interval> can improve the opportunity for |
1075 | Setting the I<timeout collect interval> can improve the opportunity for |
875 | saving power, as the program will "bundle" timer callback invocations that |
1076 | saving power, as the program will "bundle" timer callback invocations that |
876 | are "near" in time together, by delaying some, thus reducing the number of |
1077 | are "near" in time together, by delaying some, thus reducing the number of |
877 | times the process sleeps and wakes up again. Another useful technique to |
1078 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
885 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
1086 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
886 | |
1087 | |
887 | =item ev_invoke_pending (loop) |
1088 | =item ev_invoke_pending (loop) |
888 | |
1089 | |
889 | This call will simply invoke all pending watchers while resetting their |
1090 | This call will simply invoke all pending watchers while resetting their |
890 | pending state. Normally, C<ev_loop> does this automatically when required, |
1091 | pending state. Normally, C<ev_run> does this automatically when required, |
891 | but when overriding the invoke callback this call comes handy. |
1092 | but when overriding the invoke callback this call comes handy. This |
|
|
1093 | function can be invoked from a watcher - this can be useful for example |
|
|
1094 | when you want to do some lengthy calculation and want to pass further |
|
|
1095 | event handling to another thread (you still have to make sure only one |
|
|
1096 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
892 | |
1097 | |
893 | =item int ev_pending_count (loop) |
1098 | =item int ev_pending_count (loop) |
894 | |
1099 | |
895 | Returns the number of pending watchers - zero indicates that no watchers |
1100 | Returns the number of pending watchers - zero indicates that no watchers |
896 | are pending. |
1101 | are pending. |
897 | |
1102 | |
898 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
1103 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
899 | |
1104 | |
900 | This overrides the invoke pending functionality of the loop: Instead of |
1105 | This overrides the invoke pending functionality of the loop: Instead of |
901 | invoking all pending watchers when there are any, C<ev_loop> will call |
1106 | invoking all pending watchers when there are any, C<ev_run> will call |
902 | this callback instead. This is useful, for example, when you want to |
1107 | this callback instead. This is useful, for example, when you want to |
903 | invoke the actual watchers inside another context (another thread etc.). |
1108 | invoke the actual watchers inside another context (another thread etc.). |
904 | |
1109 | |
905 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1110 | If you want to reset the callback, use C<ev_invoke_pending> as new |
906 | callback. |
1111 | callback. |
907 | |
1112 | |
908 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1113 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
909 | |
1114 | |
910 | Sometimes you want to share the same loop between multiple threads. This |
1115 | Sometimes you want to share the same loop between multiple threads. This |
911 | can be done relatively simply by putting mutex_lock/unlock calls around |
1116 | can be done relatively simply by putting mutex_lock/unlock calls around |
912 | each call to a libev function. |
1117 | each call to a libev function. |
913 | |
1118 | |
914 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
1119 | However, C<ev_run> can run an indefinite time, so it is not feasible |
915 | wait for it to return. One way around this is to wake up the loop via |
1120 | to wait for it to return. One way around this is to wake up the event |
916 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
1121 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
917 | and I<acquire> callbacks on the loop. |
1122 | I<release> and I<acquire> callbacks on the loop. |
918 | |
1123 | |
919 | When set, then C<release> will be called just before the thread is |
1124 | When set, then C<release> will be called just before the thread is |
920 | suspended waiting for new events, and C<acquire> is called just |
1125 | suspended waiting for new events, and C<acquire> is called just |
921 | afterwards. |
1126 | afterwards. |
922 | |
1127 | |
… | |
… | |
925 | |
1130 | |
926 | While event loop modifications are allowed between invocations of |
1131 | While event loop modifications are allowed between invocations of |
927 | C<release> and C<acquire> (that's their only purpose after all), no |
1132 | C<release> and C<acquire> (that's their only purpose after all), no |
928 | modifications done will affect the event loop, i.e. adding watchers will |
1133 | modifications done will affect the event loop, i.e. adding watchers will |
929 | have no effect on the set of file descriptors being watched, or the time |
1134 | have no effect on the set of file descriptors being watched, or the time |
930 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
1135 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
931 | to take note of any changes you made. |
1136 | to take note of any changes you made. |
932 | |
1137 | |
933 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
1138 | In theory, threads executing C<ev_run> will be async-cancel safe between |
934 | invocations of C<release> and C<acquire>. |
1139 | invocations of C<release> and C<acquire>. |
935 | |
1140 | |
936 | See also the locking example in the C<THREADS> section later in this |
1141 | See also the locking example in the C<THREADS> section later in this |
937 | document. |
1142 | document. |
938 | |
1143 | |
939 | =item ev_set_userdata (loop, void *data) |
1144 | =item ev_set_userdata (loop, void *data) |
940 | |
1145 | |
941 | =item ev_userdata (loop) |
1146 | =item void *ev_userdata (loop) |
942 | |
1147 | |
943 | Set and retrieve a single C<void *> associated with a loop. When |
1148 | Set and retrieve a single C<void *> associated with a loop. When |
944 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1149 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
945 | C<0.> |
1150 | C<0>. |
946 | |
1151 | |
947 | These two functions can be used to associate arbitrary data with a loop, |
1152 | These two functions can be used to associate arbitrary data with a loop, |
948 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1153 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
949 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1154 | C<acquire> callbacks described above, but of course can be (ab-)used for |
950 | any other purpose as well. |
1155 | any other purpose as well. |
951 | |
1156 | |
952 | =item ev_loop_verify (loop) |
1157 | =item ev_verify (loop) |
953 | |
1158 | |
954 | This function only does something when C<EV_VERIFY> support has been |
1159 | This function only does something when C<EV_VERIFY> support has been |
955 | compiled in, which is the default for non-minimal builds. It tries to go |
1160 | compiled in, which is the default for non-minimal builds. It tries to go |
956 | through all internal structures and checks them for validity. If anything |
1161 | through all internal structures and checks them for validity. If anything |
957 | is found to be inconsistent, it will print an error message to standard |
1162 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
968 | |
1173 | |
969 | In the following description, uppercase C<TYPE> in names stands for the |
1174 | In the following description, uppercase C<TYPE> in names stands for the |
970 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1175 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
971 | watchers and C<ev_io_start> for I/O watchers. |
1176 | watchers and C<ev_io_start> for I/O watchers. |
972 | |
1177 | |
973 | A watcher is a structure that you create and register to record your |
1178 | A watcher is an opaque structure that you allocate and register to record |
974 | interest in some event. For instance, if you want to wait for STDIN to |
1179 | your interest in some event. To make a concrete example, imagine you want |
975 | become readable, you would create an C<ev_io> watcher for that: |
1180 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1181 | for that: |
976 | |
1182 | |
977 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1183 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
978 | { |
1184 | { |
979 | ev_io_stop (w); |
1185 | ev_io_stop (w); |
980 | ev_unloop (loop, EVUNLOOP_ALL); |
1186 | ev_break (loop, EVBREAK_ALL); |
981 | } |
1187 | } |
982 | |
1188 | |
983 | struct ev_loop *loop = ev_default_loop (0); |
1189 | struct ev_loop *loop = ev_default_loop (0); |
984 | |
1190 | |
985 | ev_io stdin_watcher; |
1191 | ev_io stdin_watcher; |
986 | |
1192 | |
987 | ev_init (&stdin_watcher, my_cb); |
1193 | ev_init (&stdin_watcher, my_cb); |
988 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1194 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
989 | ev_io_start (loop, &stdin_watcher); |
1195 | ev_io_start (loop, &stdin_watcher); |
990 | |
1196 | |
991 | ev_loop (loop, 0); |
1197 | ev_run (loop, 0); |
992 | |
1198 | |
993 | As you can see, you are responsible for allocating the memory for your |
1199 | As you can see, you are responsible for allocating the memory for your |
994 | watcher structures (and it is I<usually> a bad idea to do this on the |
1200 | watcher structures (and it is I<usually> a bad idea to do this on the |
995 | stack). |
1201 | stack). |
996 | |
1202 | |
997 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1203 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
998 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1204 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
999 | |
1205 | |
1000 | Each watcher structure must be initialised by a call to C<ev_init |
1206 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
1001 | (watcher *, callback)>, which expects a callback to be provided. This |
1207 | *, callback)>, which expects a callback to be provided. This callback is |
1002 | callback gets invoked each time the event occurs (or, in the case of I/O |
1208 | invoked each time the event occurs (or, in the case of I/O watchers, each |
1003 | watchers, each time the event loop detects that the file descriptor given |
1209 | time the event loop detects that the file descriptor given is readable |
1004 | is readable and/or writable). |
1210 | and/or writable). |
1005 | |
1211 | |
1006 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1212 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1007 | macro to configure it, with arguments specific to the watcher type. There |
1213 | macro to configure it, with arguments specific to the watcher type. There |
1008 | is also a macro to combine initialisation and setting in one call: C<< |
1214 | is also a macro to combine initialisation and setting in one call: C<< |
1009 | ev_TYPE_init (watcher *, callback, ...) >>. |
1215 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
1032 | =item C<EV_WRITE> |
1238 | =item C<EV_WRITE> |
1033 | |
1239 | |
1034 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1240 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1035 | writable. |
1241 | writable. |
1036 | |
1242 | |
1037 | =item C<EV_TIMEOUT> |
1243 | =item C<EV_TIMER> |
1038 | |
1244 | |
1039 | The C<ev_timer> watcher has timed out. |
1245 | The C<ev_timer> watcher has timed out. |
1040 | |
1246 | |
1041 | =item C<EV_PERIODIC> |
1247 | =item C<EV_PERIODIC> |
1042 | |
1248 | |
… | |
… | |
1060 | |
1266 | |
1061 | =item C<EV_PREPARE> |
1267 | =item C<EV_PREPARE> |
1062 | |
1268 | |
1063 | =item C<EV_CHECK> |
1269 | =item C<EV_CHECK> |
1064 | |
1270 | |
1065 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1271 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1066 | to gather new events, and all C<ev_check> watchers are invoked just after |
1272 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1067 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1273 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1274 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1275 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1276 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1277 | or lower priority within an event loop iteration. |
|
|
1278 | |
1068 | received events. Callbacks of both watcher types can start and stop as |
1279 | Callbacks of both watcher types can start and stop as many watchers as |
1069 | many watchers as they want, and all of them will be taken into account |
1280 | they want, and all of them will be taken into account (for example, a |
1070 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1281 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1071 | C<ev_loop> from blocking). |
1282 | blocking). |
1072 | |
1283 | |
1073 | =item C<EV_EMBED> |
1284 | =item C<EV_EMBED> |
1074 | |
1285 | |
1075 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1286 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1076 | |
1287 | |
1077 | =item C<EV_FORK> |
1288 | =item C<EV_FORK> |
1078 | |
1289 | |
1079 | The event loop has been resumed in the child process after fork (see |
1290 | The event loop has been resumed in the child process after fork (see |
1080 | C<ev_fork>). |
1291 | C<ev_fork>). |
|
|
1292 | |
|
|
1293 | =item C<EV_CLEANUP> |
|
|
1294 | |
|
|
1295 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1081 | |
1296 | |
1082 | =item C<EV_ASYNC> |
1297 | =item C<EV_ASYNC> |
1083 | |
1298 | |
1084 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1299 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1085 | |
1300 | |
… | |
… | |
1195 | |
1410 | |
1196 | =item callback ev_cb (ev_TYPE *watcher) |
1411 | =item callback ev_cb (ev_TYPE *watcher) |
1197 | |
1412 | |
1198 | Returns the callback currently set on the watcher. |
1413 | Returns the callback currently set on the watcher. |
1199 | |
1414 | |
1200 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1415 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1201 | |
1416 | |
1202 | Change the callback. You can change the callback at virtually any time |
1417 | Change the callback. You can change the callback at virtually any time |
1203 | (modulo threads). |
1418 | (modulo threads). |
1204 | |
1419 | |
1205 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1420 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1223 | or might not have been clamped to the valid range. |
1438 | or might not have been clamped to the valid range. |
1224 | |
1439 | |
1225 | The default priority used by watchers when no priority has been set is |
1440 | The default priority used by watchers when no priority has been set is |
1226 | always C<0>, which is supposed to not be too high and not be too low :). |
1441 | always C<0>, which is supposed to not be too high and not be too low :). |
1227 | |
1442 | |
1228 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1443 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1229 | priorities. |
1444 | priorities. |
1230 | |
1445 | |
1231 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1446 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1232 | |
1447 | |
1233 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1448 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1258 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1473 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1259 | functions that do not need a watcher. |
1474 | functions that do not need a watcher. |
1260 | |
1475 | |
1261 | =back |
1476 | =back |
1262 | |
1477 | |
|
|
1478 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1479 | OWN COMPOSITE WATCHERS> idioms. |
1263 | |
1480 | |
1264 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1481 | =head2 WATCHER STATES |
1265 | |
1482 | |
1266 | Each watcher has, by default, a member C<void *data> that you can change |
1483 | There are various watcher states mentioned throughout this manual - |
1267 | and read at any time: libev will completely ignore it. This can be used |
1484 | active, pending and so on. In this section these states and the rules to |
1268 | to associate arbitrary data with your watcher. If you need more data and |
1485 | transition between them will be described in more detail - and while these |
1269 | don't want to allocate memory and store a pointer to it in that data |
1486 | rules might look complicated, they usually do "the right thing". |
1270 | member, you can also "subclass" the watcher type and provide your own |
|
|
1271 | data: |
|
|
1272 | |
1487 | |
1273 | struct my_io |
1488 | =over 4 |
1274 | { |
|
|
1275 | ev_io io; |
|
|
1276 | int otherfd; |
|
|
1277 | void *somedata; |
|
|
1278 | struct whatever *mostinteresting; |
|
|
1279 | }; |
|
|
1280 | |
1489 | |
1281 | ... |
1490 | =item initialised |
1282 | struct my_io w; |
|
|
1283 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1284 | |
1491 | |
1285 | And since your callback will be called with a pointer to the watcher, you |
1492 | Before a watcher can be registered with the event loop it has to be |
1286 | can cast it back to your own type: |
1493 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1494 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1287 | |
1495 | |
1288 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1496 | In this state it is simply some block of memory that is suitable for |
1289 | { |
1497 | use in an event loop. It can be moved around, freed, reused etc. at |
1290 | struct my_io *w = (struct my_io *)w_; |
1498 | will - as long as you either keep the memory contents intact, or call |
1291 | ... |
1499 | C<ev_TYPE_init> again. |
1292 | } |
|
|
1293 | |
1500 | |
1294 | More interesting and less C-conformant ways of casting your callback type |
1501 | =item started/running/active |
1295 | instead have been omitted. |
|
|
1296 | |
1502 | |
1297 | Another common scenario is to use some data structure with multiple |
1503 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1298 | embedded watchers: |
1504 | property of the event loop, and is actively waiting for events. While in |
|
|
1505 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1506 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1507 | and call libev functions on it that are documented to work on active watchers. |
1299 | |
1508 | |
1300 | struct my_biggy |
1509 | =item pending |
1301 | { |
|
|
1302 | int some_data; |
|
|
1303 | ev_timer t1; |
|
|
1304 | ev_timer t2; |
|
|
1305 | } |
|
|
1306 | |
1510 | |
1307 | In this case getting the pointer to C<my_biggy> is a bit more |
1511 | If a watcher is active and libev determines that an event it is interested |
1308 | complicated: Either you store the address of your C<my_biggy> struct |
1512 | in has occurred (such as a timer expiring), it will become pending. It will |
1309 | in the C<data> member of the watcher (for woozies), or you need to use |
1513 | stay in this pending state until either it is stopped or its callback is |
1310 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1514 | about to be invoked, so it is not normally pending inside the watcher |
1311 | programmers): |
1515 | callback. |
1312 | |
1516 | |
1313 | #include <stddef.h> |
1517 | The watcher might or might not be active while it is pending (for example, |
|
|
1518 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1519 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1520 | but it is still property of the event loop at this time, so cannot be |
|
|
1521 | moved, freed or reused. And if it is active the rules described in the |
|
|
1522 | previous item still apply. |
1314 | |
1523 | |
1315 | static void |
1524 | It is also possible to feed an event on a watcher that is not active (e.g. |
1316 | t1_cb (EV_P_ ev_timer *w, int revents) |
1525 | via C<ev_feed_event>), in which case it becomes pending without being |
1317 | { |
1526 | active. |
1318 | struct my_biggy big = (struct my_biggy *) |
|
|
1319 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1320 | } |
|
|
1321 | |
1527 | |
1322 | static void |
1528 | =item stopped |
1323 | t2_cb (EV_P_ ev_timer *w, int revents) |
1529 | |
1324 | { |
1530 | A watcher can be stopped implicitly by libev (in which case it might still |
1325 | struct my_biggy big = (struct my_biggy *) |
1531 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1326 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1532 | latter will clear any pending state the watcher might be in, regardless |
1327 | } |
1533 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1534 | freeing it is often a good idea. |
|
|
1535 | |
|
|
1536 | While stopped (and not pending) the watcher is essentially in the |
|
|
1537 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1538 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1539 | it again). |
|
|
1540 | |
|
|
1541 | =back |
1328 | |
1542 | |
1329 | =head2 WATCHER PRIORITY MODELS |
1543 | =head2 WATCHER PRIORITY MODELS |
1330 | |
1544 | |
1331 | Many event loops support I<watcher priorities>, which are usually small |
1545 | Many event loops support I<watcher priorities>, which are usually small |
1332 | integers that influence the ordering of event callback invocation |
1546 | integers that influence the ordering of event callback invocation |
1333 | between watchers in some way, all else being equal. |
1547 | between watchers in some way, all else being equal. |
1334 | |
1548 | |
1335 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
1549 | In libev, watcher priorities can be set using C<ev_set_priority>. See its |
1336 | description for the more technical details such as the actual priority |
1550 | description for the more technical details such as the actual priority |
1337 | range. |
1551 | range. |
1338 | |
1552 | |
1339 | There are two common ways how these these priorities are being interpreted |
1553 | There are two common ways how these these priorities are being interpreted |
1340 | by event loops: |
1554 | by event loops: |
… | |
… | |
1375 | |
1589 | |
1376 | For example, to emulate how many other event libraries handle priorities, |
1590 | For example, to emulate how many other event libraries handle priorities, |
1377 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1591 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1378 | the normal watcher callback, you just start the idle watcher. The real |
1592 | the normal watcher callback, you just start the idle watcher. The real |
1379 | processing is done in the idle watcher callback. This causes libev to |
1593 | processing is done in the idle watcher callback. This causes libev to |
1380 | continously poll and process kernel event data for the watcher, but when |
1594 | continuously poll and process kernel event data for the watcher, but when |
1381 | the lock-out case is known to be rare (which in turn is rare :), this is |
1595 | the lock-out case is known to be rare (which in turn is rare :), this is |
1382 | workable. |
1596 | workable. |
1383 | |
1597 | |
1384 | Usually, however, the lock-out model implemented that way will perform |
1598 | Usually, however, the lock-out model implemented that way will perform |
1385 | miserably under the type of load it was designed to handle. In that case, |
1599 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1399 | { |
1613 | { |
1400 | // stop the I/O watcher, we received the event, but |
1614 | // stop the I/O watcher, we received the event, but |
1401 | // are not yet ready to handle it. |
1615 | // are not yet ready to handle it. |
1402 | ev_io_stop (EV_A_ w); |
1616 | ev_io_stop (EV_A_ w); |
1403 | |
1617 | |
1404 | // start the idle watcher to ahndle the actual event. |
1618 | // start the idle watcher to handle the actual event. |
1405 | // it will not be executed as long as other watchers |
1619 | // it will not be executed as long as other watchers |
1406 | // with the default priority are receiving events. |
1620 | // with the default priority are receiving events. |
1407 | ev_idle_start (EV_A_ &idle); |
1621 | ev_idle_start (EV_A_ &idle); |
1408 | } |
1622 | } |
1409 | |
1623 | |
… | |
… | |
1434 | |
1648 | |
1435 | This section describes each watcher in detail, but will not repeat |
1649 | This section describes each watcher in detail, but will not repeat |
1436 | information given in the last section. Any initialisation/set macros, |
1650 | information given in the last section. Any initialisation/set macros, |
1437 | functions and members specific to the watcher type are explained. |
1651 | functions and members specific to the watcher type are explained. |
1438 | |
1652 | |
1439 | Members are additionally marked with either I<[read-only]>, meaning that, |
1653 | Most members are additionally marked with either I<[read-only]>, meaning |
1440 | while the watcher is active, you can look at the member and expect some |
1654 | that, while the watcher is active, you can look at the member and expect |
1441 | sensible content, but you must not modify it (you can modify it while the |
1655 | some sensible content, but you must not modify it (you can modify it while |
1442 | watcher is stopped to your hearts content), or I<[read-write]>, which |
1656 | the watcher is stopped to your hearts content), or I<[read-write]>, which |
1443 | means you can expect it to have some sensible content while the watcher |
1657 | means you can expect it to have some sensible content while the watcher |
1444 | is active, but you can also modify it. Modifying it may not do something |
1658 | is active, but you can also modify it. Modifying it may not do something |
1445 | sensible or take immediate effect (or do anything at all), but libev will |
1659 | sensible or take immediate effect (or do anything at all), but libev will |
1446 | not crash or malfunction in any way. |
1660 | not crash or malfunction in any way. |
1447 | |
1661 | |
|
|
1662 | In any case, the documentation for each member will explain what the |
|
|
1663 | effects are, and if there are any additional access restrictions. |
1448 | |
1664 | |
1449 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1665 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1450 | |
1666 | |
1451 | I/O watchers check whether a file descriptor is readable or writable |
1667 | I/O watchers check whether a file descriptor is readable or writable |
1452 | in each iteration of the event loop, or, more precisely, when reading |
1668 | in each iteration of the event loop, or, more precisely, when reading |
… | |
… | |
1459 | In general you can register as many read and/or write event watchers per |
1675 | In general you can register as many read and/or write event watchers per |
1460 | fd as you want (as long as you don't confuse yourself). Setting all file |
1676 | fd as you want (as long as you don't confuse yourself). Setting all file |
1461 | descriptors to non-blocking mode is also usually a good idea (but not |
1677 | descriptors to non-blocking mode is also usually a good idea (but not |
1462 | required if you know what you are doing). |
1678 | required if you know what you are doing). |
1463 | |
1679 | |
1464 | If you cannot use non-blocking mode, then force the use of a |
|
|
1465 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1466 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1467 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1468 | files) - libev doesn't guarentee any specific behaviour in that case. |
|
|
1469 | |
|
|
1470 | Another thing you have to watch out for is that it is quite easy to |
1680 | Another thing you have to watch out for is that it is quite easy to |
1471 | receive "spurious" readiness notifications, that is your callback might |
1681 | receive "spurious" readiness notifications, that is, your callback might |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1682 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1473 | because there is no data. Not only are some backends known to create a |
1683 | because there is no data. It is very easy to get into this situation even |
1474 | lot of those (for example Solaris ports), it is very easy to get into |
1684 | with a relatively standard program structure. Thus it is best to always |
1475 | this situation even with a relatively standard program structure. Thus |
1685 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1476 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1477 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1686 | preferable to a program hanging until some data arrives. |
1478 | |
1687 | |
1479 | If you cannot run the fd in non-blocking mode (for example you should |
1688 | If you cannot run the fd in non-blocking mode (for example you should |
1480 | not play around with an Xlib connection), then you have to separately |
1689 | not play around with an Xlib connection), then you have to separately |
1481 | re-test whether a file descriptor is really ready with a known-to-be good |
1690 | re-test whether a file descriptor is really ready with a known-to-be good |
1482 | interface such as poll (fortunately in our Xlib example, Xlib already |
1691 | interface such as poll (fortunately in the case of Xlib, it already does |
1483 | does this on its own, so its quite safe to use). Some people additionally |
1692 | this on its own, so its quite safe to use). Some people additionally |
1484 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1693 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1485 | indefinitely. |
1694 | indefinitely. |
1486 | |
1695 | |
1487 | But really, best use non-blocking mode. |
1696 | But really, best use non-blocking mode. |
1488 | |
1697 | |
1489 | =head3 The special problem of disappearing file descriptors |
1698 | =head3 The special problem of disappearing file descriptors |
1490 | |
1699 | |
1491 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1700 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1492 | descriptor (either due to calling C<close> explicitly or any other means, |
1701 | a file descriptor (either due to calling C<close> explicitly or any other |
1493 | such as C<dup2>). The reason is that you register interest in some file |
1702 | means, such as C<dup2>). The reason is that you register interest in some |
1494 | descriptor, but when it goes away, the operating system will silently drop |
1703 | file descriptor, but when it goes away, the operating system will silently |
1495 | this interest. If another file descriptor with the same number then is |
1704 | drop this interest. If another file descriptor with the same number then |
1496 | registered with libev, there is no efficient way to see that this is, in |
1705 | is registered with libev, there is no efficient way to see that this is, |
1497 | fact, a different file descriptor. |
1706 | in fact, a different file descriptor. |
1498 | |
1707 | |
1499 | To avoid having to explicitly tell libev about such cases, libev follows |
1708 | To avoid having to explicitly tell libev about such cases, libev follows |
1500 | the following policy: Each time C<ev_io_set> is being called, libev |
1709 | the following policy: Each time C<ev_io_set> is being called, libev |
1501 | will assume that this is potentially a new file descriptor, otherwise |
1710 | will assume that this is potentially a new file descriptor, otherwise |
1502 | it is assumed that the file descriptor stays the same. That means that |
1711 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1516 | |
1725 | |
1517 | There is no workaround possible except not registering events |
1726 | There is no workaround possible except not registering events |
1518 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1727 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1519 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1728 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1520 | |
1729 | |
|
|
1730 | =head3 The special problem of files |
|
|
1731 | |
|
|
1732 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1733 | representing files, and expect it to become ready when their program |
|
|
1734 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1735 | |
|
|
1736 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1737 | notification as soon as the kernel knows whether and how much data is |
|
|
1738 | there, and in the case of open files, that's always the case, so you |
|
|
1739 | always get a readiness notification instantly, and your read (or possibly |
|
|
1740 | write) will still block on the disk I/O. |
|
|
1741 | |
|
|
1742 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1743 | devices and so on, there is another party (the sender) that delivers data |
|
|
1744 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1745 | will not send data on its own, simply because it doesn't know what you |
|
|
1746 | wish to read - you would first have to request some data. |
|
|
1747 | |
|
|
1748 | Since files are typically not-so-well supported by advanced notification |
|
|
1749 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1750 | to files, even though you should not use it. The reason for this is |
|
|
1751 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1752 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1753 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1754 | F</dev/urandom>), and even though the file might better be served with |
|
|
1755 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1756 | it "just works" instead of freezing. |
|
|
1757 | |
|
|
1758 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1759 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1760 | when you rarely read from a file instead of from a socket, and want to |
|
|
1761 | reuse the same code path. |
|
|
1762 | |
1521 | =head3 The special problem of fork |
1763 | =head3 The special problem of fork |
1522 | |
1764 | |
1523 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1765 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1524 | useless behaviour. Libev fully supports fork, but needs to be told about |
1766 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1525 | it in the child. |
1767 | to be told about it in the child if you want to continue to use it in the |
|
|
1768 | child. |
1526 | |
1769 | |
1527 | To support fork in your programs, you either have to call |
1770 | To support fork in your child processes, you have to call C<ev_loop_fork |
1528 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1771 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1529 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1772 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1530 | C<EVBACKEND_POLL>. |
|
|
1531 | |
1773 | |
1532 | =head3 The special problem of SIGPIPE |
1774 | =head3 The special problem of SIGPIPE |
1533 | |
1775 | |
1534 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1776 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1535 | when writing to a pipe whose other end has been closed, your program gets |
1777 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1541 | somewhere, as that would have given you a big clue). |
1783 | somewhere, as that would have given you a big clue). |
1542 | |
1784 | |
1543 | =head3 The special problem of accept()ing when you can't |
1785 | =head3 The special problem of accept()ing when you can't |
1544 | |
1786 | |
1545 | Many implementations of the POSIX C<accept> function (for example, |
1787 | Many implementations of the POSIX C<accept> function (for example, |
1546 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
1788 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
1547 | connection from the pending queue in all error cases. |
1789 | connection from the pending queue in all error cases. |
1548 | |
1790 | |
1549 | For example, larger servers often run out of file descriptors (because |
1791 | For example, larger servers often run out of file descriptors (because |
1550 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1792 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1551 | rejecting the connection, leading to libev signalling readiness on |
1793 | rejecting the connection, leading to libev signalling readiness on |
… | |
… | |
1589 | |
1831 | |
1590 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1832 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1591 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1833 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1592 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1834 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1593 | |
1835 | |
1594 | =item int fd [read-only] |
1836 | =item ev_io_modify (ev_io *, int events) |
1595 | |
1837 | |
1596 | The file descriptor being watched. |
1838 | Similar to C<ev_io_set>, but only changes the event mask. Using this might |
|
|
1839 | be faster with some backends, as libev can assume that the C<fd> still |
|
|
1840 | refers to the same underlying file description, something it cannot do |
|
|
1841 | when using C<ev_io_set>. |
1597 | |
1842 | |
|
|
1843 | =item int fd [no-modify] |
|
|
1844 | |
|
|
1845 | The file descriptor being watched. While it can be read at any time, you |
|
|
1846 | must not modify this member even when the watcher is stopped - always use |
|
|
1847 | C<ev_io_set> for that. |
|
|
1848 | |
1598 | =item int events [read-only] |
1849 | =item int events [no-modify] |
1599 | |
1850 | |
1600 | The events being watched. |
1851 | The set of events being watched, among other flags. This field is a |
|
|
1852 | bit set - to test for C<EV_READ>, use C<< w->events & EV_READ >>, and |
|
|
1853 | similarly for C<EV_WRITE>. |
|
|
1854 | |
|
|
1855 | As with C<fd>, you must not modify this member even when the watcher is |
|
|
1856 | stopped, always use C<ev_io_set> or C<ev_io_modify> for that. |
1601 | |
1857 | |
1602 | =back |
1858 | =back |
1603 | |
1859 | |
1604 | =head3 Examples |
1860 | =head3 Examples |
1605 | |
1861 | |
… | |
… | |
1617 | ... |
1873 | ... |
1618 | struct ev_loop *loop = ev_default_init (0); |
1874 | struct ev_loop *loop = ev_default_init (0); |
1619 | ev_io stdin_readable; |
1875 | ev_io stdin_readable; |
1620 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1876 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1621 | ev_io_start (loop, &stdin_readable); |
1877 | ev_io_start (loop, &stdin_readable); |
1622 | ev_loop (loop, 0); |
1878 | ev_run (loop, 0); |
1623 | |
1879 | |
1624 | |
1880 | |
1625 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1881 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1626 | |
1882 | |
1627 | Timer watchers are simple relative timers that generate an event after a |
1883 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1633 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1889 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1634 | monotonic clock option helps a lot here). |
1890 | monotonic clock option helps a lot here). |
1635 | |
1891 | |
1636 | The callback is guaranteed to be invoked only I<after> its timeout has |
1892 | The callback is guaranteed to be invoked only I<after> its timeout has |
1637 | passed (not I<at>, so on systems with very low-resolution clocks this |
1893 | passed (not I<at>, so on systems with very low-resolution clocks this |
1638 | might introduce a small delay). If multiple timers become ready during the |
1894 | might introduce a small delay, see "the special problem of being too |
|
|
1895 | early", below). If multiple timers become ready during the same loop |
1639 | same loop iteration then the ones with earlier time-out values are invoked |
1896 | iteration then the ones with earlier time-out values are invoked before |
1640 | before ones of the same priority with later time-out values (but this is |
1897 | ones of the same priority with later time-out values (but this is no |
1641 | no longer true when a callback calls C<ev_loop> recursively). |
1898 | longer true when a callback calls C<ev_run> recursively). |
1642 | |
1899 | |
1643 | =head3 Be smart about timeouts |
1900 | =head3 Be smart about timeouts |
1644 | |
1901 | |
1645 | Many real-world problems involve some kind of timeout, usually for error |
1902 | Many real-world problems involve some kind of timeout, usually for error |
1646 | recovery. A typical example is an HTTP request - if the other side hangs, |
1903 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1721 | |
1978 | |
1722 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1979 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1723 | but remember the time of last activity, and check for a real timeout only |
1980 | but remember the time of last activity, and check for a real timeout only |
1724 | within the callback: |
1981 | within the callback: |
1725 | |
1982 | |
|
|
1983 | ev_tstamp timeout = 60.; |
1726 | ev_tstamp last_activity; // time of last activity |
1984 | ev_tstamp last_activity; // time of last activity |
|
|
1985 | ev_timer timer; |
1727 | |
1986 | |
1728 | static void |
1987 | static void |
1729 | callback (EV_P_ ev_timer *w, int revents) |
1988 | callback (EV_P_ ev_timer *w, int revents) |
1730 | { |
1989 | { |
1731 | ev_tstamp now = ev_now (EV_A); |
1990 | // calculate when the timeout would happen |
1732 | ev_tstamp timeout = last_activity + 60.; |
1991 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1733 | |
1992 | |
1734 | // if last_activity + 60. is older than now, we did time out |
1993 | // if negative, it means we the timeout already occurred |
1735 | if (timeout < now) |
1994 | if (after < 0.) |
1736 | { |
1995 | { |
1737 | // timeout occured, take action |
1996 | // timeout occurred, take action |
1738 | } |
1997 | } |
1739 | else |
1998 | else |
1740 | { |
1999 | { |
1741 | // callback was invoked, but there was some activity, re-arm |
2000 | // callback was invoked, but there was some recent |
1742 | // the watcher to fire in last_activity + 60, which is |
2001 | // activity. simply restart the timer to time out |
1743 | // guaranteed to be in the future, so "again" is positive: |
2002 | // after "after" seconds, which is the earliest time |
1744 | w->repeat = timeout - now; |
2003 | // the timeout can occur. |
|
|
2004 | ev_timer_set (w, after, 0.); |
1745 | ev_timer_again (EV_A_ w); |
2005 | ev_timer_start (EV_A_ w); |
1746 | } |
2006 | } |
1747 | } |
2007 | } |
1748 | |
2008 | |
1749 | To summarise the callback: first calculate the real timeout (defined |
2009 | To summarise the callback: first calculate in how many seconds the |
1750 | as "60 seconds after the last activity"), then check if that time has |
2010 | timeout will occur (by calculating the absolute time when it would occur, |
1751 | been reached, which means something I<did>, in fact, time out. Otherwise |
2011 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1752 | the callback was invoked too early (C<timeout> is in the future), so |
2012 | (EV_A)> from that). |
1753 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1754 | a timeout then. |
|
|
1755 | |
2013 | |
1756 | Note how C<ev_timer_again> is used, taking advantage of the |
2014 | If this value is negative, then we are already past the timeout, i.e. we |
1757 | C<ev_timer_again> optimisation when the timer is already running. |
2015 | timed out, and need to do whatever is needed in this case. |
|
|
2016 | |
|
|
2017 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2018 | and simply start the timer with this timeout value. |
|
|
2019 | |
|
|
2020 | In other words, each time the callback is invoked it will check whether |
|
|
2021 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
2022 | again at the earliest time it could time out. Rinse. Repeat. |
1758 | |
2023 | |
1759 | This scheme causes more callback invocations (about one every 60 seconds |
2024 | This scheme causes more callback invocations (about one every 60 seconds |
1760 | minus half the average time between activity), but virtually no calls to |
2025 | minus half the average time between activity), but virtually no calls to |
1761 | libev to change the timeout. |
2026 | libev to change the timeout. |
1762 | |
2027 | |
1763 | To start the timer, simply initialise the watcher and set C<last_activity> |
2028 | To start the machinery, simply initialise the watcher and set |
1764 | to the current time (meaning we just have some activity :), then call the |
2029 | C<last_activity> to the current time (meaning there was some activity just |
1765 | callback, which will "do the right thing" and start the timer: |
2030 | now), then call the callback, which will "do the right thing" and start |
|
|
2031 | the timer: |
1766 | |
2032 | |
|
|
2033 | last_activity = ev_now (EV_A); |
1767 | ev_init (timer, callback); |
2034 | ev_init (&timer, callback); |
1768 | last_activity = ev_now (loop); |
2035 | callback (EV_A_ &timer, 0); |
1769 | callback (loop, timer, EV_TIMEOUT); |
|
|
1770 | |
2036 | |
1771 | And when there is some activity, simply store the current time in |
2037 | When there is some activity, simply store the current time in |
1772 | C<last_activity>, no libev calls at all: |
2038 | C<last_activity>, no libev calls at all: |
1773 | |
2039 | |
|
|
2040 | if (activity detected) |
1774 | last_actiivty = ev_now (loop); |
2041 | last_activity = ev_now (EV_A); |
|
|
2042 | |
|
|
2043 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2044 | providing a new value, stopping the timer and calling the callback, which |
|
|
2045 | will again do the right thing (for example, time out immediately :). |
|
|
2046 | |
|
|
2047 | timeout = new_value; |
|
|
2048 | ev_timer_stop (EV_A_ &timer); |
|
|
2049 | callback (EV_A_ &timer, 0); |
1775 | |
2050 | |
1776 | This technique is slightly more complex, but in most cases where the |
2051 | This technique is slightly more complex, but in most cases where the |
1777 | time-out is unlikely to be triggered, much more efficient. |
2052 | time-out is unlikely to be triggered, much more efficient. |
1778 | |
|
|
1779 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1780 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1781 | fix things for you. |
|
|
1782 | |
2053 | |
1783 | =item 4. Wee, just use a double-linked list for your timeouts. |
2054 | =item 4. Wee, just use a double-linked list for your timeouts. |
1784 | |
2055 | |
1785 | If there is not one request, but many thousands (millions...), all |
2056 | If there is not one request, but many thousands (millions...), all |
1786 | employing some kind of timeout with the same timeout value, then one can |
2057 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1813 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2084 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1814 | rather complicated, but extremely efficient, something that really pays |
2085 | rather complicated, but extremely efficient, something that really pays |
1815 | off after the first million or so of active timers, i.e. it's usually |
2086 | off after the first million or so of active timers, i.e. it's usually |
1816 | overkill :) |
2087 | overkill :) |
1817 | |
2088 | |
|
|
2089 | =head3 The special problem of being too early |
|
|
2090 | |
|
|
2091 | If you ask a timer to call your callback after three seconds, then |
|
|
2092 | you expect it to be invoked after three seconds - but of course, this |
|
|
2093 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2094 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2095 | process with a STOP signal for a few hours for example. |
|
|
2096 | |
|
|
2097 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2098 | delay has occurred, but cannot guarantee this. |
|
|
2099 | |
|
|
2100 | A less obvious failure mode is calling your callback too early: many event |
|
|
2101 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2102 | this can cause your callback to be invoked much earlier than you would |
|
|
2103 | expect. |
|
|
2104 | |
|
|
2105 | To see why, imagine a system with a clock that only offers full second |
|
|
2106 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2107 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2108 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2109 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2110 | |
|
|
2111 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2112 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2113 | one-second delay was requested - this is being "too early", despite best |
|
|
2114 | intentions. |
|
|
2115 | |
|
|
2116 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2117 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2118 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2119 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2120 | |
|
|
2121 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2122 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2123 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2124 | late" side of things. |
|
|
2125 | |
1818 | =head3 The special problem of time updates |
2126 | =head3 The special problem of time updates |
1819 | |
2127 | |
1820 | Establishing the current time is a costly operation (it usually takes at |
2128 | Establishing the current time is a costly operation (it usually takes |
1821 | least two system calls): EV therefore updates its idea of the current |
2129 | at least one system call): EV therefore updates its idea of the current |
1822 | time only before and after C<ev_loop> collects new events, which causes a |
2130 | time only before and after C<ev_run> collects new events, which causes a |
1823 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2131 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1824 | lots of events in one iteration. |
2132 | lots of events in one iteration. |
1825 | |
2133 | |
1826 | The relative timeouts are calculated relative to the C<ev_now ()> |
2134 | The relative timeouts are calculated relative to the C<ev_now ()> |
1827 | time. This is usually the right thing as this timestamp refers to the time |
2135 | time. This is usually the right thing as this timestamp refers to the time |
1828 | of the event triggering whatever timeout you are modifying/starting. If |
2136 | of the event triggering whatever timeout you are modifying/starting. If |
1829 | you suspect event processing to be delayed and you I<need> to base the |
2137 | you suspect event processing to be delayed and you I<need> to base the |
1830 | timeout on the current time, use something like this to adjust for this: |
2138 | timeout on the current time, use something like the following to adjust |
|
|
2139 | for it: |
1831 | |
2140 | |
1832 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2141 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1833 | |
2142 | |
1834 | If the event loop is suspended for a long time, you can also force an |
2143 | If the event loop is suspended for a long time, you can also force an |
1835 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2144 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1836 | ()>. |
2145 | ()>, although that will push the event time of all outstanding events |
|
|
2146 | further into the future. |
|
|
2147 | |
|
|
2148 | =head3 The special problem of unsynchronised clocks |
|
|
2149 | |
|
|
2150 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2151 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2152 | jumps). |
|
|
2153 | |
|
|
2154 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2155 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2156 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2157 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2158 | than a directly following call to C<time>. |
|
|
2159 | |
|
|
2160 | The moral of this is to only compare libev-related timestamps with |
|
|
2161 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2162 | a second or so. |
|
|
2163 | |
|
|
2164 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2165 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2166 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2167 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2168 | |
|
|
2169 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2170 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2171 | I<measured according to the real time>, not the system clock. |
|
|
2172 | |
|
|
2173 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2174 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2175 | exactly the right behaviour. |
|
|
2176 | |
|
|
2177 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2178 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2179 | time, where your comparisons will always generate correct results. |
1837 | |
2180 | |
1838 | =head3 The special problems of suspended animation |
2181 | =head3 The special problems of suspended animation |
1839 | |
2182 | |
1840 | When you leave the server world it is quite customary to hit machines that |
2183 | When you leave the server world it is quite customary to hit machines that |
1841 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2184 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1871 | |
2214 | |
1872 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2215 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1873 | |
2216 | |
1874 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2217 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1875 | |
2218 | |
1876 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2219 | Configure the timer to trigger after C<after> seconds (fractional and |
1877 | is C<0.>, then it will automatically be stopped once the timeout is |
2220 | negative values are supported). If C<repeat> is C<0.>, then it will |
1878 | reached. If it is positive, then the timer will automatically be |
2221 | automatically be stopped once the timeout is reached. If it is positive, |
1879 | configured to trigger again C<repeat> seconds later, again, and again, |
2222 | then the timer will automatically be configured to trigger again C<repeat> |
1880 | until stopped manually. |
2223 | seconds later, again, and again, until stopped manually. |
1881 | |
2224 | |
1882 | The timer itself will do a best-effort at avoiding drift, that is, if |
2225 | The timer itself will do a best-effort at avoiding drift, that is, if |
1883 | you configure a timer to trigger every 10 seconds, then it will normally |
2226 | you configure a timer to trigger every 10 seconds, then it will normally |
1884 | trigger at exactly 10 second intervals. If, however, your program cannot |
2227 | trigger at exactly 10 second intervals. If, however, your program cannot |
1885 | keep up with the timer (because it takes longer than those 10 seconds to |
2228 | keep up with the timer (because it takes longer than those 10 seconds to |
1886 | do stuff) the timer will not fire more than once per event loop iteration. |
2229 | do stuff) the timer will not fire more than once per event loop iteration. |
1887 | |
2230 | |
1888 | =item ev_timer_again (loop, ev_timer *) |
2231 | =item ev_timer_again (loop, ev_timer *) |
1889 | |
2232 | |
1890 | This will act as if the timer timed out and restart it again if it is |
2233 | This will act as if the timer timed out, and restarts it again if it is |
1891 | repeating. The exact semantics are: |
2234 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2235 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1892 | |
2236 | |
|
|
2237 | The exact semantics are as in the following rules, all of which will be |
|
|
2238 | applied to the watcher: |
|
|
2239 | |
|
|
2240 | =over 4 |
|
|
2241 | |
1893 | If the timer is pending, its pending status is cleared. |
2242 | =item If the timer is pending, the pending status is always cleared. |
1894 | |
2243 | |
1895 | If the timer is started but non-repeating, stop it (as if it timed out). |
2244 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2245 | out, without invoking it). |
1896 | |
2246 | |
1897 | If the timer is repeating, either start it if necessary (with the |
2247 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1898 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2248 | and start the timer, if necessary. |
1899 | |
2249 | |
|
|
2250 | =back |
|
|
2251 | |
1900 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2252 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1901 | usage example. |
2253 | usage example. |
1902 | |
2254 | |
1903 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2255 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1904 | |
2256 | |
1905 | Returns the remaining time until a timer fires. If the timer is active, |
2257 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
1944 | } |
2296 | } |
1945 | |
2297 | |
1946 | ev_timer mytimer; |
2298 | ev_timer mytimer; |
1947 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2299 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1948 | ev_timer_again (&mytimer); /* start timer */ |
2300 | ev_timer_again (&mytimer); /* start timer */ |
1949 | ev_loop (loop, 0); |
2301 | ev_run (loop, 0); |
1950 | |
2302 | |
1951 | // and in some piece of code that gets executed on any "activity": |
2303 | // and in some piece of code that gets executed on any "activity": |
1952 | // reset the timeout to start ticking again at 10 seconds |
2304 | // reset the timeout to start ticking again at 10 seconds |
1953 | ev_timer_again (&mytimer); |
2305 | ev_timer_again (&mytimer); |
1954 | |
2306 | |
… | |
… | |
1958 | Periodic watchers are also timers of a kind, but they are very versatile |
2310 | Periodic watchers are also timers of a kind, but they are very versatile |
1959 | (and unfortunately a bit complex). |
2311 | (and unfortunately a bit complex). |
1960 | |
2312 | |
1961 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2313 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1962 | relative time, the physical time that passes) but on wall clock time |
2314 | relative time, the physical time that passes) but on wall clock time |
1963 | (absolute time, the thing you can read on your calender or clock). The |
2315 | (absolute time, the thing you can read on your calendar or clock). The |
1964 | difference is that wall clock time can run faster or slower than real |
2316 | difference is that wall clock time can run faster or slower than real |
1965 | time, and time jumps are not uncommon (e.g. when you adjust your |
2317 | time, and time jumps are not uncommon (e.g. when you adjust your |
1966 | wrist-watch). |
2318 | wrist-watch). |
1967 | |
2319 | |
1968 | You can tell a periodic watcher to trigger after some specific point |
2320 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
1973 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2325 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
1974 | it, as it uses a relative timeout). |
2326 | it, as it uses a relative timeout). |
1975 | |
2327 | |
1976 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2328 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1977 | timers, such as triggering an event on each "midnight, local time", or |
2329 | timers, such as triggering an event on each "midnight, local time", or |
1978 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2330 | other complicated rules. This cannot easily be done with C<ev_timer> |
1979 | those cannot react to time jumps. |
2331 | watchers, as those cannot react to time jumps. |
1980 | |
2332 | |
1981 | As with timers, the callback is guaranteed to be invoked only when the |
2333 | As with timers, the callback is guaranteed to be invoked only when the |
1982 | point in time where it is supposed to trigger has passed. If multiple |
2334 | point in time where it is supposed to trigger has passed. If multiple |
1983 | timers become ready during the same loop iteration then the ones with |
2335 | timers become ready during the same loop iteration then the ones with |
1984 | earlier time-out values are invoked before ones with later time-out values |
2336 | earlier time-out values are invoked before ones with later time-out values |
1985 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
2337 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1986 | |
2338 | |
1987 | =head3 Watcher-Specific Functions and Data Members |
2339 | =head3 Watcher-Specific Functions and Data Members |
1988 | |
2340 | |
1989 | =over 4 |
2341 | =over 4 |
1990 | |
2342 | |
… | |
… | |
2025 | |
2377 | |
2026 | Another way to think about it (for the mathematically inclined) is that |
2378 | Another way to think about it (for the mathematically inclined) is that |
2027 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2379 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2028 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2380 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2029 | |
2381 | |
2030 | For numerical stability it is preferable that the C<offset> value is near |
2382 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2031 | C<ev_now ()> (the current time), but there is no range requirement for |
2383 | interval value should be higher than C<1/8192> (which is around 100 |
2032 | this value, and in fact is often specified as zero. |
2384 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2385 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2386 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2387 | C<0> and C<interval>, which is also the recommended range. |
2033 | |
2388 | |
2034 | Note also that there is an upper limit to how often a timer can fire (CPU |
2389 | Note also that there is an upper limit to how often a timer can fire (CPU |
2035 | speed for example), so if C<interval> is very small then timing stability |
2390 | speed for example), so if C<interval> is very small then timing stability |
2036 | will of course deteriorate. Libev itself tries to be exact to be about one |
2391 | will of course deteriorate. Libev itself tries to be exact to be about one |
2037 | millisecond (if the OS supports it and the machine is fast enough). |
2392 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2067 | |
2422 | |
2068 | NOTE: I<< This callback must always return a time that is higher than or |
2423 | NOTE: I<< This callback must always return a time that is higher than or |
2069 | equal to the passed C<now> value >>. |
2424 | equal to the passed C<now> value >>. |
2070 | |
2425 | |
2071 | This can be used to create very complex timers, such as a timer that |
2426 | This can be used to create very complex timers, such as a timer that |
2072 | triggers on "next midnight, local time". To do this, you would calculate the |
2427 | triggers on "next midnight, local time". To do this, you would calculate |
2073 | next midnight after C<now> and return the timestamp value for this. How |
2428 | the next midnight after C<now> and return the timestamp value for |
2074 | you do this is, again, up to you (but it is not trivial, which is the main |
2429 | this. Here is a (completely untested, no error checking) example on how to |
2075 | reason I omitted it as an example). |
2430 | do this: |
|
|
2431 | |
|
|
2432 | #include <time.h> |
|
|
2433 | |
|
|
2434 | static ev_tstamp |
|
|
2435 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2436 | { |
|
|
2437 | time_t tnow = (time_t)now; |
|
|
2438 | struct tm tm; |
|
|
2439 | localtime_r (&tnow, &tm); |
|
|
2440 | |
|
|
2441 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2442 | ++tm.tm_mday; // midnight next day |
|
|
2443 | |
|
|
2444 | return mktime (&tm); |
|
|
2445 | } |
|
|
2446 | |
|
|
2447 | Note: this code might run into trouble on days that have more then two |
|
|
2448 | midnights (beginning and end). |
2076 | |
2449 | |
2077 | =back |
2450 | =back |
2078 | |
2451 | |
2079 | =item ev_periodic_again (loop, ev_periodic *) |
2452 | =item ev_periodic_again (loop, ev_periodic *) |
2080 | |
2453 | |
… | |
… | |
2118 | Example: Call a callback every hour, or, more precisely, whenever the |
2491 | Example: Call a callback every hour, or, more precisely, whenever the |
2119 | system time is divisible by 3600. The callback invocation times have |
2492 | system time is divisible by 3600. The callback invocation times have |
2120 | potentially a lot of jitter, but good long-term stability. |
2493 | potentially a lot of jitter, but good long-term stability. |
2121 | |
2494 | |
2122 | static void |
2495 | static void |
2123 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2496 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2124 | { |
2497 | { |
2125 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2498 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2126 | } |
2499 | } |
2127 | |
2500 | |
2128 | ev_periodic hourly_tick; |
2501 | ev_periodic hourly_tick; |
… | |
… | |
2145 | |
2518 | |
2146 | ev_periodic hourly_tick; |
2519 | ev_periodic hourly_tick; |
2147 | ev_periodic_init (&hourly_tick, clock_cb, |
2520 | ev_periodic_init (&hourly_tick, clock_cb, |
2148 | fmod (ev_now (loop), 3600.), 3600., 0); |
2521 | fmod (ev_now (loop), 3600.), 3600., 0); |
2149 | ev_periodic_start (loop, &hourly_tick); |
2522 | ev_periodic_start (loop, &hourly_tick); |
2150 | |
2523 | |
2151 | |
2524 | |
2152 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2525 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2153 | |
2526 | |
2154 | Signal watchers will trigger an event when the process receives a specific |
2527 | Signal watchers will trigger an event when the process receives a specific |
2155 | signal one or more times. Even though signals are very asynchronous, libev |
2528 | signal one or more times. Even though signals are very asynchronous, libev |
2156 | will try it's best to deliver signals synchronously, i.e. as part of the |
2529 | will try its best to deliver signals synchronously, i.e. as part of the |
2157 | normal event processing, like any other event. |
2530 | normal event processing, like any other event. |
2158 | |
2531 | |
2159 | If you want signals to be delivered truly asynchronously, just use |
2532 | If you want signals to be delivered truly asynchronously, just use |
2160 | C<sigaction> as you would do without libev and forget about sharing |
2533 | C<sigaction> as you would do without libev and forget about sharing |
2161 | the signal. You can even use C<ev_async> from a signal handler to |
2534 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2165 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2538 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2166 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2539 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2167 | C<SIGINT> in both the default loop and another loop at the same time. At |
2540 | C<SIGINT> in both the default loop and another loop at the same time. At |
2168 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2541 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2169 | |
2542 | |
2170 | When the first watcher gets started will libev actually register something |
2543 | Only after the first watcher for a signal is started will libev actually |
2171 | with the kernel (thus it coexists with your own signal handlers as long as |
2544 | register something with the kernel. It thus coexists with your own signal |
2172 | you don't register any with libev for the same signal). |
2545 | handlers as long as you don't register any with libev for the same signal. |
2173 | |
2546 | |
2174 | If possible and supported, libev will install its handlers with |
2547 | If possible and supported, libev will install its handlers with |
2175 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2548 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2176 | not be unduly interrupted. If you have a problem with system calls getting |
2549 | not be unduly interrupted. If you have a problem with system calls getting |
2177 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2550 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2180 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2553 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2181 | |
2554 | |
2182 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2555 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2183 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2556 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2184 | stopping it again), that is, libev might or might not block the signal, |
2557 | stopping it again), that is, libev might or might not block the signal, |
2185 | and might or might not set or restore the installed signal handler. |
2558 | and might or might not set or restore the installed signal handler (but |
|
|
2559 | see C<EVFLAG_NOSIGMASK>). |
2186 | |
2560 | |
2187 | While this does not matter for the signal disposition (libev never |
2561 | While this does not matter for the signal disposition (libev never |
2188 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2562 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2189 | C<execve>), this matters for the signal mask: many programs do not expect |
2563 | C<execve>), this matters for the signal mask: many programs do not expect |
2190 | certain signals to be blocked. |
2564 | certain signals to be blocked. |
… | |
… | |
2204 | |
2578 | |
2205 | So I can't stress this enough: I<If you do not reset your signal mask when |
2579 | So I can't stress this enough: I<If you do not reset your signal mask when |
2206 | you expect it to be empty, you have a race condition in your code>. This |
2580 | you expect it to be empty, you have a race condition in your code>. This |
2207 | is not a libev-specific thing, this is true for most event libraries. |
2581 | is not a libev-specific thing, this is true for most event libraries. |
2208 | |
2582 | |
|
|
2583 | =head3 The special problem of threads signal handling |
|
|
2584 | |
|
|
2585 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2586 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2587 | threads in a process block signals, which is hard to achieve. |
|
|
2588 | |
|
|
2589 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2590 | for the same signals), you can tackle this problem by globally blocking |
|
|
2591 | all signals before creating any threads (or creating them with a fully set |
|
|
2592 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2593 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2594 | these signals. You can pass on any signals that libev might be interested |
|
|
2595 | in by calling C<ev_feed_signal>. |
|
|
2596 | |
2209 | =head3 Watcher-Specific Functions and Data Members |
2597 | =head3 Watcher-Specific Functions and Data Members |
2210 | |
2598 | |
2211 | =over 4 |
2599 | =over 4 |
2212 | |
2600 | |
2213 | =item ev_signal_init (ev_signal *, callback, int signum) |
2601 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
2228 | Example: Try to exit cleanly on SIGINT. |
2616 | Example: Try to exit cleanly on SIGINT. |
2229 | |
2617 | |
2230 | static void |
2618 | static void |
2231 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2619 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2232 | { |
2620 | { |
2233 | ev_unloop (loop, EVUNLOOP_ALL); |
2621 | ev_break (loop, EVBREAK_ALL); |
2234 | } |
2622 | } |
2235 | |
2623 | |
2236 | ev_signal signal_watcher; |
2624 | ev_signal signal_watcher; |
2237 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2625 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2238 | ev_signal_start (loop, &signal_watcher); |
2626 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
2347 | |
2735 | |
2348 | =head2 C<ev_stat> - did the file attributes just change? |
2736 | =head2 C<ev_stat> - did the file attributes just change? |
2349 | |
2737 | |
2350 | This watches a file system path for attribute changes. That is, it calls |
2738 | This watches a file system path for attribute changes. That is, it calls |
2351 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2739 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2352 | and sees if it changed compared to the last time, invoking the callback if |
2740 | and sees if it changed compared to the last time, invoking the callback |
2353 | it did. |
2741 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2742 | happen after the watcher has been started will be reported. |
2354 | |
2743 | |
2355 | The path does not need to exist: changing from "path exists" to "path does |
2744 | The path does not need to exist: changing from "path exists" to "path does |
2356 | not exist" is a status change like any other. The condition "path does not |
2745 | not exist" is a status change like any other. The condition "path does not |
2357 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2746 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2358 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2747 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2588 | Apart from keeping your process non-blocking (which is a useful |
2977 | Apart from keeping your process non-blocking (which is a useful |
2589 | effect on its own sometimes), idle watchers are a good place to do |
2978 | effect on its own sometimes), idle watchers are a good place to do |
2590 | "pseudo-background processing", or delay processing stuff to after the |
2979 | "pseudo-background processing", or delay processing stuff to after the |
2591 | event loop has handled all outstanding events. |
2980 | event loop has handled all outstanding events. |
2592 | |
2981 | |
|
|
2982 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2983 | |
|
|
2984 | As long as there is at least one active idle watcher, libev will never |
|
|
2985 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2986 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2987 | lowest priority will do. |
|
|
2988 | |
|
|
2989 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2990 | to do something on each event loop iteration - for example to balance load |
|
|
2991 | between different connections. |
|
|
2992 | |
|
|
2993 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2994 | example. |
|
|
2995 | |
2593 | =head3 Watcher-Specific Functions and Data Members |
2996 | =head3 Watcher-Specific Functions and Data Members |
2594 | |
2997 | |
2595 | =over 4 |
2998 | =over 4 |
2596 | |
2999 | |
2597 | =item ev_idle_init (ev_idle *, callback) |
3000 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2608 | callback, free it. Also, use no error checking, as usual. |
3011 | callback, free it. Also, use no error checking, as usual. |
2609 | |
3012 | |
2610 | static void |
3013 | static void |
2611 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
3014 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2612 | { |
3015 | { |
|
|
3016 | // stop the watcher |
|
|
3017 | ev_idle_stop (loop, w); |
|
|
3018 | |
|
|
3019 | // now we can free it |
2613 | free (w); |
3020 | free (w); |
|
|
3021 | |
2614 | // now do something you wanted to do when the program has |
3022 | // now do something you wanted to do when the program has |
2615 | // no longer anything immediate to do. |
3023 | // no longer anything immediate to do. |
2616 | } |
3024 | } |
2617 | |
3025 | |
2618 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
3026 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2620 | ev_idle_start (loop, idle_watcher); |
3028 | ev_idle_start (loop, idle_watcher); |
2621 | |
3029 | |
2622 | |
3030 | |
2623 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3031 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2624 | |
3032 | |
2625 | Prepare and check watchers are usually (but not always) used in pairs: |
3033 | Prepare and check watchers are often (but not always) used in pairs: |
2626 | prepare watchers get invoked before the process blocks and check watchers |
3034 | prepare watchers get invoked before the process blocks and check watchers |
2627 | afterwards. |
3035 | afterwards. |
2628 | |
3036 | |
2629 | You I<must not> call C<ev_loop> or similar functions that enter |
3037 | You I<must not> call C<ev_run> (or similar functions that enter the |
2630 | the current event loop from either C<ev_prepare> or C<ev_check> |
3038 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2631 | watchers. Other loops than the current one are fine, however. The |
3039 | C<ev_check> watchers. Other loops than the current one are fine, |
2632 | rationale behind this is that you do not need to check for recursion in |
3040 | however. The rationale behind this is that you do not need to check |
2633 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3041 | for recursion in those watchers, i.e. the sequence will always be |
2634 | C<ev_check> so if you have one watcher of each kind they will always be |
3042 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2635 | called in pairs bracketing the blocking call. |
3043 | kind they will always be called in pairs bracketing the blocking call. |
2636 | |
3044 | |
2637 | Their main purpose is to integrate other event mechanisms into libev and |
3045 | Their main purpose is to integrate other event mechanisms into libev and |
2638 | their use is somewhat advanced. They could be used, for example, to track |
3046 | their use is somewhat advanced. They could be used, for example, to track |
2639 | variable changes, implement your own watchers, integrate net-snmp or a |
3047 | variable changes, implement your own watchers, integrate net-snmp or a |
2640 | coroutine library and lots more. They are also occasionally useful if |
3048 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2658 | with priority higher than or equal to the event loop and one coroutine |
3066 | with priority higher than or equal to the event loop and one coroutine |
2659 | of lower priority, but only once, using idle watchers to keep the event |
3067 | of lower priority, but only once, using idle watchers to keep the event |
2660 | loop from blocking if lower-priority coroutines are active, thus mapping |
3068 | loop from blocking if lower-priority coroutines are active, thus mapping |
2661 | low-priority coroutines to idle/background tasks). |
3069 | low-priority coroutines to idle/background tasks). |
2662 | |
3070 | |
2663 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3071 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2664 | priority, to ensure that they are being run before any other watchers |
3072 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2665 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3073 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3074 | watchers). |
2666 | |
3075 | |
2667 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3076 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2668 | activate ("feed") events into libev. While libev fully supports this, they |
3077 | activate ("feed") events into libev. While libev fully supports this, they |
2669 | might get executed before other C<ev_check> watchers did their job. As |
3078 | might get executed before other C<ev_check> watchers did their job. As |
2670 | C<ev_check> watchers are often used to embed other (non-libev) event |
3079 | C<ev_check> watchers are often used to embed other (non-libev) event |
2671 | loops those other event loops might be in an unusable state until their |
3080 | loops those other event loops might be in an unusable state until their |
2672 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3081 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2673 | others). |
3082 | others). |
|
|
3083 | |
|
|
3084 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3085 | |
|
|
3086 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3087 | useful because they are called once per event loop iteration. For |
|
|
3088 | example, if you want to handle a large number of connections fairly, you |
|
|
3089 | normally only do a bit of work for each active connection, and if there |
|
|
3090 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3091 | connections have a chance of making progress. |
|
|
3092 | |
|
|
3093 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3094 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3095 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3096 | |
|
|
3097 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3098 | single global idle watcher that is active as long as you have one active |
|
|
3099 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3100 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3101 | invoked. Neither watcher alone can do that. |
2674 | |
3102 | |
2675 | =head3 Watcher-Specific Functions and Data Members |
3103 | =head3 Watcher-Specific Functions and Data Members |
2676 | |
3104 | |
2677 | =over 4 |
3105 | =over 4 |
2678 | |
3106 | |
… | |
… | |
2802 | |
3230 | |
2803 | if (timeout >= 0) |
3231 | if (timeout >= 0) |
2804 | // create/start timer |
3232 | // create/start timer |
2805 | |
3233 | |
2806 | // poll |
3234 | // poll |
2807 | ev_loop (EV_A_ 0); |
3235 | ev_run (EV_A_ 0); |
2808 | |
3236 | |
2809 | // stop timer again |
3237 | // stop timer again |
2810 | if (timeout >= 0) |
3238 | if (timeout >= 0) |
2811 | ev_timer_stop (EV_A_ &to); |
3239 | ev_timer_stop (EV_A_ &to); |
2812 | |
3240 | |
… | |
… | |
2879 | |
3307 | |
2880 | =over 4 |
3308 | =over 4 |
2881 | |
3309 | |
2882 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3310 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2883 | |
3311 | |
2884 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3312 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2885 | |
3313 | |
2886 | Configures the watcher to embed the given loop, which must be |
3314 | Configures the watcher to embed the given loop, which must be |
2887 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3315 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2888 | invoked automatically, otherwise it is the responsibility of the callback |
3316 | invoked automatically, otherwise it is the responsibility of the callback |
2889 | to invoke it (it will continue to be called until the sweep has been done, |
3317 | to invoke it (it will continue to be called until the sweep has been done, |
2890 | if you do not want that, you need to temporarily stop the embed watcher). |
3318 | if you do not want that, you need to temporarily stop the embed watcher). |
2891 | |
3319 | |
2892 | =item ev_embed_sweep (loop, ev_embed *) |
3320 | =item ev_embed_sweep (loop, ev_embed *) |
2893 | |
3321 | |
2894 | Make a single, non-blocking sweep over the embedded loop. This works |
3322 | Make a single, non-blocking sweep over the embedded loop. This works |
2895 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3323 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2896 | appropriate way for embedded loops. |
3324 | appropriate way for embedded loops. |
2897 | |
3325 | |
2898 | =item struct ev_loop *other [read-only] |
3326 | =item struct ev_loop *other [read-only] |
2899 | |
3327 | |
2900 | The embedded event loop. |
3328 | The embedded event loop. |
… | |
… | |
2910 | used). |
3338 | used). |
2911 | |
3339 | |
2912 | struct ev_loop *loop_hi = ev_default_init (0); |
3340 | struct ev_loop *loop_hi = ev_default_init (0); |
2913 | struct ev_loop *loop_lo = 0; |
3341 | struct ev_loop *loop_lo = 0; |
2914 | ev_embed embed; |
3342 | ev_embed embed; |
2915 | |
3343 | |
2916 | // see if there is a chance of getting one that works |
3344 | // see if there is a chance of getting one that works |
2917 | // (remember that a flags value of 0 means autodetection) |
3345 | // (remember that a flags value of 0 means autodetection) |
2918 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3346 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2919 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3347 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2920 | : 0; |
3348 | : 0; |
… | |
… | |
2934 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3362 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2935 | |
3363 | |
2936 | struct ev_loop *loop = ev_default_init (0); |
3364 | struct ev_loop *loop = ev_default_init (0); |
2937 | struct ev_loop *loop_socket = 0; |
3365 | struct ev_loop *loop_socket = 0; |
2938 | ev_embed embed; |
3366 | ev_embed embed; |
2939 | |
3367 | |
2940 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3368 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2941 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3369 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2942 | { |
3370 | { |
2943 | ev_embed_init (&embed, 0, loop_socket); |
3371 | ev_embed_init (&embed, 0, loop_socket); |
2944 | ev_embed_start (loop, &embed); |
3372 | ev_embed_start (loop, &embed); |
… | |
… | |
2952 | |
3380 | |
2953 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3381 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2954 | |
3382 | |
2955 | Fork watchers are called when a C<fork ()> was detected (usually because |
3383 | Fork watchers are called when a C<fork ()> was detected (usually because |
2956 | whoever is a good citizen cared to tell libev about it by calling |
3384 | whoever is a good citizen cared to tell libev about it by calling |
2957 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3385 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
2958 | event loop blocks next and before C<ev_check> watchers are being called, |
3386 | and before C<ev_check> watchers are being called, and only in the child |
2959 | and only in the child after the fork. If whoever good citizen calling |
3387 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
2960 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3388 | and calls it in the wrong process, the fork handlers will be invoked, too, |
2961 | handlers will be invoked, too, of course. |
3389 | of course. |
2962 | |
3390 | |
2963 | =head3 The special problem of life after fork - how is it possible? |
3391 | =head3 The special problem of life after fork - how is it possible? |
2964 | |
3392 | |
2965 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
3393 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
2966 | up/change the process environment, followed by a call to C<exec()>. This |
3394 | up/change the process environment, followed by a call to C<exec()>. This |
2967 | sequence should be handled by libev without any problems. |
3395 | sequence should be handled by libev without any problems. |
2968 | |
3396 | |
2969 | This changes when the application actually wants to do event handling |
3397 | This changes when the application actually wants to do event handling |
2970 | in the child, or both parent in child, in effect "continuing" after the |
3398 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2986 | disadvantage of having to use multiple event loops (which do not support |
3414 | disadvantage of having to use multiple event loops (which do not support |
2987 | signal watchers). |
3415 | signal watchers). |
2988 | |
3416 | |
2989 | When this is not possible, or you want to use the default loop for |
3417 | When this is not possible, or you want to use the default loop for |
2990 | other reasons, then in the process that wants to start "fresh", call |
3418 | other reasons, then in the process that wants to start "fresh", call |
2991 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3419 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
2992 | the default loop will "orphan" (not stop) all registered watchers, so you |
3420 | Destroying the default loop will "orphan" (not stop) all registered |
2993 | have to be careful not to execute code that modifies those watchers. Note |
3421 | watchers, so you have to be careful not to execute code that modifies |
2994 | also that in that case, you have to re-register any signal watchers. |
3422 | those watchers. Note also that in that case, you have to re-register any |
|
|
3423 | signal watchers. |
2995 | |
3424 | |
2996 | =head3 Watcher-Specific Functions and Data Members |
3425 | =head3 Watcher-Specific Functions and Data Members |
2997 | |
3426 | |
2998 | =over 4 |
3427 | =over 4 |
2999 | |
3428 | |
3000 | =item ev_fork_init (ev_signal *, callback) |
3429 | =item ev_fork_init (ev_fork *, callback) |
3001 | |
3430 | |
3002 | Initialises and configures the fork watcher - it has no parameters of any |
3431 | Initialises and configures the fork watcher - it has no parameters of any |
3003 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3432 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3004 | believe me. |
3433 | really. |
3005 | |
3434 | |
3006 | =back |
3435 | =back |
3007 | |
3436 | |
3008 | |
3437 | |
|
|
3438 | =head2 C<ev_cleanup> - even the best things end |
|
|
3439 | |
|
|
3440 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3441 | by a call to C<ev_loop_destroy>. |
|
|
3442 | |
|
|
3443 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3444 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3445 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3446 | loop when you want them to be invoked. |
|
|
3447 | |
|
|
3448 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3449 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3450 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3451 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3452 | |
|
|
3453 | =head3 Watcher-Specific Functions and Data Members |
|
|
3454 | |
|
|
3455 | =over 4 |
|
|
3456 | |
|
|
3457 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3458 | |
|
|
3459 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3460 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3461 | pointless, I assure you. |
|
|
3462 | |
|
|
3463 | =back |
|
|
3464 | |
|
|
3465 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3466 | cleanup functions are called. |
|
|
3467 | |
|
|
3468 | static void |
|
|
3469 | program_exits (void) |
|
|
3470 | { |
|
|
3471 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3472 | } |
|
|
3473 | |
|
|
3474 | ... |
|
|
3475 | atexit (program_exits); |
|
|
3476 | |
|
|
3477 | |
3009 | =head2 C<ev_async> - how to wake up another event loop |
3478 | =head2 C<ev_async> - how to wake up an event loop |
3010 | |
3479 | |
3011 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3480 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3012 | asynchronous sources such as signal handlers (as opposed to multiple event |
3481 | asynchronous sources such as signal handlers (as opposed to multiple event |
3013 | loops - those are of course safe to use in different threads). |
3482 | loops - those are of course safe to use in different threads). |
3014 | |
3483 | |
3015 | Sometimes, however, you need to wake up another event loop you do not |
3484 | Sometimes, however, you need to wake up an event loop you do not control, |
3016 | control, for example because it belongs to another thread. This is what |
3485 | for example because it belongs to another thread. This is what C<ev_async> |
3017 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3486 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
3018 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3487 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3019 | safe. |
|
|
3020 | |
3488 | |
3021 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3489 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3022 | too, are asynchronous in nature, and signals, too, will be compressed |
3490 | too, are asynchronous in nature, and signals, too, will be compressed |
3023 | (i.e. the number of callback invocations may be less than the number of |
3491 | (i.e. the number of callback invocations may be less than the number of |
3024 | C<ev_async_sent> calls). |
3492 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3025 | |
3493 | of "global async watchers" by using a watcher on an otherwise unused |
3026 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3494 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3027 | just the default loop. |
3495 | even without knowing which loop owns the signal. |
3028 | |
3496 | |
3029 | =head3 Queueing |
3497 | =head3 Queueing |
3030 | |
3498 | |
3031 | C<ev_async> does not support queueing of data in any way. The reason |
3499 | C<ev_async> does not support queueing of data in any way. The reason |
3032 | is that the author does not know of a simple (or any) algorithm for a |
3500 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3124 | trust me. |
3592 | trust me. |
3125 | |
3593 | |
3126 | =item ev_async_send (loop, ev_async *) |
3594 | =item ev_async_send (loop, ev_async *) |
3127 | |
3595 | |
3128 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3596 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3129 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3597 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3598 | returns. |
|
|
3599 | |
3130 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3600 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3131 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3601 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3132 | section below on what exactly this means). |
3602 | embedding section below on what exactly this means). |
3133 | |
3603 | |
3134 | Note that, as with other watchers in libev, multiple events might get |
3604 | Note that, as with other watchers in libev, multiple events might get |
3135 | compressed into a single callback invocation (another way to look at this |
3605 | compressed into a single callback invocation (another way to look at |
3136 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3606 | this is that C<ev_async> watchers are level-triggered: they are set on |
3137 | reset when the event loop detects that). |
3607 | C<ev_async_send>, reset when the event loop detects that). |
3138 | |
3608 | |
3139 | This call incurs the overhead of a system call only once per event loop |
3609 | This call incurs the overhead of at most one extra system call per event |
3140 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3610 | loop iteration, if the event loop is blocked, and no syscall at all if |
3141 | repeated calls to C<ev_async_send> for the same event loop. |
3611 | the event loop (or your program) is processing events. That means that |
|
|
3612 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3613 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3614 | zero) under load. |
3142 | |
3615 | |
3143 | =item bool = ev_async_pending (ev_async *) |
3616 | =item bool = ev_async_pending (ev_async *) |
3144 | |
3617 | |
3145 | Returns a non-zero value when C<ev_async_send> has been called on the |
3618 | Returns a non-zero value when C<ev_async_send> has been called on the |
3146 | watcher but the event has not yet been processed (or even noted) by the |
3619 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3163 | |
3636 | |
3164 | There are some other functions of possible interest. Described. Here. Now. |
3637 | There are some other functions of possible interest. Described. Here. Now. |
3165 | |
3638 | |
3166 | =over 4 |
3639 | =over 4 |
3167 | |
3640 | |
3168 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3641 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3169 | |
3642 | |
3170 | This function combines a simple timer and an I/O watcher, calls your |
3643 | This function combines a simple timer and an I/O watcher, calls your |
3171 | callback on whichever event happens first and automatically stops both |
3644 | callback on whichever event happens first and automatically stops both |
3172 | watchers. This is useful if you want to wait for a single event on an fd |
3645 | watchers. This is useful if you want to wait for a single event on an fd |
3173 | or timeout without having to allocate/configure/start/stop/free one or |
3646 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3179 | |
3652 | |
3180 | If C<timeout> is less than 0, then no timeout watcher will be |
3653 | If C<timeout> is less than 0, then no timeout watcher will be |
3181 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3654 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3182 | repeat = 0) will be started. C<0> is a valid timeout. |
3655 | repeat = 0) will be started. C<0> is a valid timeout. |
3183 | |
3656 | |
3184 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3657 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3185 | passed an C<revents> set like normal event callbacks (a combination of |
3658 | passed an C<revents> set like normal event callbacks (a combination of |
3186 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3659 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3187 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3660 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3188 | a timeout and an io event at the same time - you probably should give io |
3661 | a timeout and an io event at the same time - you probably should give io |
3189 | events precedence. |
3662 | events precedence. |
3190 | |
3663 | |
3191 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3664 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3192 | |
3665 | |
3193 | static void stdin_ready (int revents, void *arg) |
3666 | static void stdin_ready (int revents, void *arg) |
3194 | { |
3667 | { |
3195 | if (revents & EV_READ) |
3668 | if (revents & EV_READ) |
3196 | /* stdin might have data for us, joy! */; |
3669 | /* stdin might have data for us, joy! */; |
3197 | else if (revents & EV_TIMEOUT) |
3670 | else if (revents & EV_TIMER) |
3198 | /* doh, nothing entered */; |
3671 | /* doh, nothing entered */; |
3199 | } |
3672 | } |
3200 | |
3673 | |
3201 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3674 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3202 | |
3675 | |
3203 | =item ev_feed_fd_event (loop, int fd, int revents) |
3676 | =item ev_feed_fd_event (loop, int fd, int revents) |
3204 | |
3677 | |
3205 | Feed an event on the given fd, as if a file descriptor backend detected |
3678 | Feed an event on the given fd, as if a file descriptor backend detected |
3206 | the given events it. |
3679 | the given events. |
3207 | |
3680 | |
3208 | =item ev_feed_signal_event (loop, int signum) |
3681 | =item ev_feed_signal_event (loop, int signum) |
3209 | |
3682 | |
3210 | Feed an event as if the given signal occurred (C<loop> must be the default |
3683 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3211 | loop!). |
3684 | which is async-safe. |
3212 | |
3685 | |
3213 | =back |
3686 | =back |
|
|
3687 | |
|
|
3688 | |
|
|
3689 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3690 | |
|
|
3691 | This section explains some common idioms that are not immediately |
|
|
3692 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3693 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3694 | |
|
|
3695 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3696 | |
|
|
3697 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3698 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3699 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3700 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3701 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3702 | data: |
|
|
3703 | |
|
|
3704 | struct my_io |
|
|
3705 | { |
|
|
3706 | ev_io io; |
|
|
3707 | int otherfd; |
|
|
3708 | void *somedata; |
|
|
3709 | struct whatever *mostinteresting; |
|
|
3710 | }; |
|
|
3711 | |
|
|
3712 | ... |
|
|
3713 | struct my_io w; |
|
|
3714 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3715 | |
|
|
3716 | And since your callback will be called with a pointer to the watcher, you |
|
|
3717 | can cast it back to your own type: |
|
|
3718 | |
|
|
3719 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3720 | { |
|
|
3721 | struct my_io *w = (struct my_io *)w_; |
|
|
3722 | ... |
|
|
3723 | } |
|
|
3724 | |
|
|
3725 | More interesting and less C-conformant ways of casting your callback |
|
|
3726 | function type instead have been omitted. |
|
|
3727 | |
|
|
3728 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3729 | |
|
|
3730 | Another common scenario is to use some data structure with multiple |
|
|
3731 | embedded watchers, in effect creating your own watcher that combines |
|
|
3732 | multiple libev event sources into one "super-watcher": |
|
|
3733 | |
|
|
3734 | struct my_biggy |
|
|
3735 | { |
|
|
3736 | int some_data; |
|
|
3737 | ev_timer t1; |
|
|
3738 | ev_timer t2; |
|
|
3739 | } |
|
|
3740 | |
|
|
3741 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3742 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3743 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3744 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3745 | real programmers): |
|
|
3746 | |
|
|
3747 | #include <stddef.h> |
|
|
3748 | |
|
|
3749 | static void |
|
|
3750 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3751 | { |
|
|
3752 | struct my_biggy big = (struct my_biggy *) |
|
|
3753 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3754 | } |
|
|
3755 | |
|
|
3756 | static void |
|
|
3757 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3758 | { |
|
|
3759 | struct my_biggy big = (struct my_biggy *) |
|
|
3760 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3761 | } |
|
|
3762 | |
|
|
3763 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3764 | |
|
|
3765 | Often you have structures like this in event-based programs: |
|
|
3766 | |
|
|
3767 | callback () |
|
|
3768 | { |
|
|
3769 | free (request); |
|
|
3770 | } |
|
|
3771 | |
|
|
3772 | request = start_new_request (..., callback); |
|
|
3773 | |
|
|
3774 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3775 | used to cancel the operation, or do other things with it. |
|
|
3776 | |
|
|
3777 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3778 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3779 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3780 | operation and simply invoke the callback with the result. |
|
|
3781 | |
|
|
3782 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3783 | has returned, so C<request> is not set. |
|
|
3784 | |
|
|
3785 | Even if you pass the request by some safer means to the callback, you |
|
|
3786 | might want to do something to the request after starting it, such as |
|
|
3787 | canceling it, which probably isn't working so well when the callback has |
|
|
3788 | already been invoked. |
|
|
3789 | |
|
|
3790 | A common way around all these issues is to make sure that |
|
|
3791 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3792 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3793 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3794 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3795 | pushing it into the pending queue: |
|
|
3796 | |
|
|
3797 | ev_set_cb (watcher, callback); |
|
|
3798 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3799 | |
|
|
3800 | This way, C<start_new_request> can safely return before the callback is |
|
|
3801 | invoked, while not delaying callback invocation too much. |
|
|
3802 | |
|
|
3803 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3804 | |
|
|
3805 | Often (especially in GUI toolkits) there are places where you have |
|
|
3806 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3807 | invoking C<ev_run>. |
|
|
3808 | |
|
|
3809 | This brings the problem of exiting - a callback might want to finish the |
|
|
3810 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3811 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3812 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3813 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3814 | |
|
|
3815 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3816 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3817 | triggered, using C<EVRUN_ONCE>: |
|
|
3818 | |
|
|
3819 | // main loop |
|
|
3820 | int exit_main_loop = 0; |
|
|
3821 | |
|
|
3822 | while (!exit_main_loop) |
|
|
3823 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3824 | |
|
|
3825 | // in a modal watcher |
|
|
3826 | int exit_nested_loop = 0; |
|
|
3827 | |
|
|
3828 | while (!exit_nested_loop) |
|
|
3829 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3830 | |
|
|
3831 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3832 | |
|
|
3833 | // exit modal loop |
|
|
3834 | exit_nested_loop = 1; |
|
|
3835 | |
|
|
3836 | // exit main program, after modal loop is finished |
|
|
3837 | exit_main_loop = 1; |
|
|
3838 | |
|
|
3839 | // exit both |
|
|
3840 | exit_main_loop = exit_nested_loop = 1; |
|
|
3841 | |
|
|
3842 | =head2 THREAD LOCKING EXAMPLE |
|
|
3843 | |
|
|
3844 | Here is a fictitious example of how to run an event loop in a different |
|
|
3845 | thread from where callbacks are being invoked and watchers are |
|
|
3846 | created/added/removed. |
|
|
3847 | |
|
|
3848 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3849 | which uses exactly this technique (which is suited for many high-level |
|
|
3850 | languages). |
|
|
3851 | |
|
|
3852 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3853 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3854 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3855 | |
|
|
3856 | First, you need to associate some data with the event loop: |
|
|
3857 | |
|
|
3858 | typedef struct { |
|
|
3859 | mutex_t lock; /* global loop lock */ |
|
|
3860 | ev_async async_w; |
|
|
3861 | thread_t tid; |
|
|
3862 | cond_t invoke_cv; |
|
|
3863 | } userdata; |
|
|
3864 | |
|
|
3865 | void prepare_loop (EV_P) |
|
|
3866 | { |
|
|
3867 | // for simplicity, we use a static userdata struct. |
|
|
3868 | static userdata u; |
|
|
3869 | |
|
|
3870 | ev_async_init (&u->async_w, async_cb); |
|
|
3871 | ev_async_start (EV_A_ &u->async_w); |
|
|
3872 | |
|
|
3873 | pthread_mutex_init (&u->lock, 0); |
|
|
3874 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3875 | |
|
|
3876 | // now associate this with the loop |
|
|
3877 | ev_set_userdata (EV_A_ u); |
|
|
3878 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3879 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3880 | |
|
|
3881 | // then create the thread running ev_run |
|
|
3882 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3883 | } |
|
|
3884 | |
|
|
3885 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3886 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3887 | that might have been added: |
|
|
3888 | |
|
|
3889 | static void |
|
|
3890 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3891 | { |
|
|
3892 | // just used for the side effects |
|
|
3893 | } |
|
|
3894 | |
|
|
3895 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3896 | protecting the loop data, respectively. |
|
|
3897 | |
|
|
3898 | static void |
|
|
3899 | l_release (EV_P) |
|
|
3900 | { |
|
|
3901 | userdata *u = ev_userdata (EV_A); |
|
|
3902 | pthread_mutex_unlock (&u->lock); |
|
|
3903 | } |
|
|
3904 | |
|
|
3905 | static void |
|
|
3906 | l_acquire (EV_P) |
|
|
3907 | { |
|
|
3908 | userdata *u = ev_userdata (EV_A); |
|
|
3909 | pthread_mutex_lock (&u->lock); |
|
|
3910 | } |
|
|
3911 | |
|
|
3912 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3913 | into C<ev_run>: |
|
|
3914 | |
|
|
3915 | void * |
|
|
3916 | l_run (void *thr_arg) |
|
|
3917 | { |
|
|
3918 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3919 | |
|
|
3920 | l_acquire (EV_A); |
|
|
3921 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3922 | ev_run (EV_A_ 0); |
|
|
3923 | l_release (EV_A); |
|
|
3924 | |
|
|
3925 | return 0; |
|
|
3926 | } |
|
|
3927 | |
|
|
3928 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3929 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3930 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3931 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3932 | and b) skipping inter-thread-communication when there are no pending |
|
|
3933 | watchers is very beneficial): |
|
|
3934 | |
|
|
3935 | static void |
|
|
3936 | l_invoke (EV_P) |
|
|
3937 | { |
|
|
3938 | userdata *u = ev_userdata (EV_A); |
|
|
3939 | |
|
|
3940 | while (ev_pending_count (EV_A)) |
|
|
3941 | { |
|
|
3942 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3943 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3944 | } |
|
|
3945 | } |
|
|
3946 | |
|
|
3947 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3948 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3949 | thread to continue: |
|
|
3950 | |
|
|
3951 | static void |
|
|
3952 | real_invoke_pending (EV_P) |
|
|
3953 | { |
|
|
3954 | userdata *u = ev_userdata (EV_A); |
|
|
3955 | |
|
|
3956 | pthread_mutex_lock (&u->lock); |
|
|
3957 | ev_invoke_pending (EV_A); |
|
|
3958 | pthread_cond_signal (&u->invoke_cv); |
|
|
3959 | pthread_mutex_unlock (&u->lock); |
|
|
3960 | } |
|
|
3961 | |
|
|
3962 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3963 | event loop, you will now have to lock: |
|
|
3964 | |
|
|
3965 | ev_timer timeout_watcher; |
|
|
3966 | userdata *u = ev_userdata (EV_A); |
|
|
3967 | |
|
|
3968 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3969 | |
|
|
3970 | pthread_mutex_lock (&u->lock); |
|
|
3971 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3972 | ev_async_send (EV_A_ &u->async_w); |
|
|
3973 | pthread_mutex_unlock (&u->lock); |
|
|
3974 | |
|
|
3975 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3976 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3977 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3978 | watchers in the next event loop iteration. |
|
|
3979 | |
|
|
3980 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3981 | |
|
|
3982 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3983 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3984 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3985 | doesn't need callbacks anymore. |
|
|
3986 | |
|
|
3987 | Imagine you have coroutines that you can switch to using a function |
|
|
3988 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3989 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3990 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3991 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3992 | the differing C<;> conventions): |
|
|
3993 | |
|
|
3994 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3995 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3996 | |
|
|
3997 | That means instead of having a C callback function, you store the |
|
|
3998 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3999 | your callback, you instead have it switch to that coroutine. |
|
|
4000 | |
|
|
4001 | A coroutine might now wait for an event with a function called |
|
|
4002 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
4003 | matter when, or whether the watcher is active or not when this function is |
|
|
4004 | called): |
|
|
4005 | |
|
|
4006 | void |
|
|
4007 | wait_for_event (ev_watcher *w) |
|
|
4008 | { |
|
|
4009 | ev_set_cb (w, current_coro); |
|
|
4010 | switch_to (libev_coro); |
|
|
4011 | } |
|
|
4012 | |
|
|
4013 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
4014 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
4015 | this or any other coroutine. |
|
|
4016 | |
|
|
4017 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
4018 | instead of storing a coroutine, you store the queue object and instead of |
|
|
4019 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
4020 | any waiters. |
|
|
4021 | |
|
|
4022 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
4023 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
4024 | |
|
|
4025 | // my_ev.h |
|
|
4026 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
4027 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
4028 | #include "../libev/ev.h" |
|
|
4029 | |
|
|
4030 | // my_ev.c |
|
|
4031 | #define EV_H "my_ev.h" |
|
|
4032 | #include "../libev/ev.c" |
|
|
4033 | |
|
|
4034 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
4035 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
4036 | can even use F<ev.h> as header file name directly. |
3214 | |
4037 | |
3215 | |
4038 | |
3216 | =head1 LIBEVENT EMULATION |
4039 | =head1 LIBEVENT EMULATION |
3217 | |
4040 | |
3218 | Libev offers a compatibility emulation layer for libevent. It cannot |
4041 | Libev offers a compatibility emulation layer for libevent. It cannot |
3219 | emulate the internals of libevent, so here are some usage hints: |
4042 | emulate the internals of libevent, so here are some usage hints: |
3220 | |
4043 | |
3221 | =over 4 |
4044 | =over 4 |
|
|
4045 | |
|
|
4046 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
4047 | |
|
|
4048 | This was the newest libevent version available when libev was implemented, |
|
|
4049 | and is still mostly unchanged in 2010. |
3222 | |
4050 | |
3223 | =item * Use it by including <event.h>, as usual. |
4051 | =item * Use it by including <event.h>, as usual. |
3224 | |
4052 | |
3225 | =item * The following members are fully supported: ev_base, ev_callback, |
4053 | =item * The following members are fully supported: ev_base, ev_callback, |
3226 | ev_arg, ev_fd, ev_res, ev_events. |
4054 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3232 | =item * Priorities are not currently supported. Initialising priorities |
4060 | =item * Priorities are not currently supported. Initialising priorities |
3233 | will fail and all watchers will have the same priority, even though there |
4061 | will fail and all watchers will have the same priority, even though there |
3234 | is an ev_pri field. |
4062 | is an ev_pri field. |
3235 | |
4063 | |
3236 | =item * In libevent, the last base created gets the signals, in libev, the |
4064 | =item * In libevent, the last base created gets the signals, in libev, the |
3237 | first base created (== the default loop) gets the signals. |
4065 | base that registered the signal gets the signals. |
3238 | |
4066 | |
3239 | =item * Other members are not supported. |
4067 | =item * Other members are not supported. |
3240 | |
4068 | |
3241 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
4069 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3242 | to use the libev header file and library. |
4070 | to use the libev header file and library. |
3243 | |
4071 | |
3244 | =back |
4072 | =back |
3245 | |
4073 | |
3246 | =head1 C++ SUPPORT |
4074 | =head1 C++ SUPPORT |
|
|
4075 | |
|
|
4076 | =head2 C API |
|
|
4077 | |
|
|
4078 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4079 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4080 | will work fine. |
|
|
4081 | |
|
|
4082 | Proper exception specifications might have to be added to callbacks passed |
|
|
4083 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4084 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4085 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4086 | specification. If you have code that needs to be compiled as both C and |
|
|
4087 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4088 | |
|
|
4089 | static void |
|
|
4090 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4091 | { |
|
|
4092 | perror (msg); |
|
|
4093 | abort (); |
|
|
4094 | } |
|
|
4095 | |
|
|
4096 | ... |
|
|
4097 | ev_set_syserr_cb (fatal_error); |
|
|
4098 | |
|
|
4099 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4100 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4101 | because it runs cleanup watchers). |
|
|
4102 | |
|
|
4103 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4104 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4105 | throwing exceptions through C libraries (most do). |
|
|
4106 | |
|
|
4107 | =head2 C++ API |
3247 | |
4108 | |
3248 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4109 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3249 | you to use some convenience methods to start/stop watchers and also change |
4110 | you to use some convenience methods to start/stop watchers and also change |
3250 | the callback model to a model using method callbacks on objects. |
4111 | the callback model to a model using method callbacks on objects. |
3251 | |
4112 | |
3252 | To use it, |
4113 | To use it, |
3253 | |
4114 | |
3254 | #include <ev++.h> |
4115 | #include <ev++.h> |
3255 | |
4116 | |
3256 | This automatically includes F<ev.h> and puts all of its definitions (many |
4117 | This automatically includes F<ev.h> and puts all of its definitions (many |
3257 | of them macros) into the global namespace. All C++ specific things are |
4118 | of them macros) into the global namespace. All C++ specific things are |
3258 | put into the C<ev> namespace. It should support all the same embedding |
4119 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3261 | Care has been taken to keep the overhead low. The only data member the C++ |
4122 | Care has been taken to keep the overhead low. The only data member the C++ |
3262 | classes add (compared to plain C-style watchers) is the event loop pointer |
4123 | classes add (compared to plain C-style watchers) is the event loop pointer |
3263 | that the watcher is associated with (or no additional members at all if |
4124 | that the watcher is associated with (or no additional members at all if |
3264 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4125 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3265 | |
4126 | |
3266 | Currently, functions, and static and non-static member functions can be |
4127 | Currently, functions, static and non-static member functions and classes |
3267 | used as callbacks. Other types should be easy to add as long as they only |
4128 | with C<operator ()> can be used as callbacks. Other types should be easy |
3268 | need one additional pointer for context. If you need support for other |
4129 | to add as long as they only need one additional pointer for context. If |
3269 | types of functors please contact the author (preferably after implementing |
4130 | you need support for other types of functors please contact the author |
3270 | it). |
4131 | (preferably after implementing it). |
|
|
4132 | |
|
|
4133 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4134 | conventions as your C compiler (for static member functions), or you have |
|
|
4135 | to embed libev and compile libev itself as C++. |
3271 | |
4136 | |
3272 | Here is a list of things available in the C<ev> namespace: |
4137 | Here is a list of things available in the C<ev> namespace: |
3273 | |
4138 | |
3274 | =over 4 |
4139 | =over 4 |
3275 | |
4140 | |
… | |
… | |
3285 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4150 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3286 | |
4151 | |
3287 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4152 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3288 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4153 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3289 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4154 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3290 | defines by many implementations. |
4155 | defined by many implementations. |
3291 | |
4156 | |
3292 | All of those classes have these methods: |
4157 | All of those classes have these methods: |
3293 | |
4158 | |
3294 | =over 4 |
4159 | =over 4 |
3295 | |
4160 | |
… | |
… | |
3336 | myclass obj; |
4201 | myclass obj; |
3337 | ev::io iow; |
4202 | ev::io iow; |
3338 | iow.set <myclass, &myclass::io_cb> (&obj); |
4203 | iow.set <myclass, &myclass::io_cb> (&obj); |
3339 | |
4204 | |
3340 | =item w->set (object *) |
4205 | =item w->set (object *) |
3341 | |
|
|
3342 | This is an B<experimental> feature that might go away in a future version. |
|
|
3343 | |
4206 | |
3344 | This is a variation of a method callback - leaving out the method to call |
4207 | This is a variation of a method callback - leaving out the method to call |
3345 | will default the method to C<operator ()>, which makes it possible to use |
4208 | will default the method to C<operator ()>, which makes it possible to use |
3346 | functor objects without having to manually specify the C<operator ()> all |
4209 | functor objects without having to manually specify the C<operator ()> all |
3347 | the time. Incidentally, you can then also leave out the template argument |
4210 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3359 | void operator() (ev::io &w, int revents) |
4222 | void operator() (ev::io &w, int revents) |
3360 | { |
4223 | { |
3361 | ... |
4224 | ... |
3362 | } |
4225 | } |
3363 | } |
4226 | } |
3364 | |
4227 | |
3365 | myfunctor f; |
4228 | myfunctor f; |
3366 | |
4229 | |
3367 | ev::io w; |
4230 | ev::io w; |
3368 | w.set (&f); |
4231 | w.set (&f); |
3369 | |
4232 | |
… | |
… | |
3387 | Associates a different C<struct ev_loop> with this watcher. You can only |
4250 | Associates a different C<struct ev_loop> with this watcher. You can only |
3388 | do this when the watcher is inactive (and not pending either). |
4251 | do this when the watcher is inactive (and not pending either). |
3389 | |
4252 | |
3390 | =item w->set ([arguments]) |
4253 | =item w->set ([arguments]) |
3391 | |
4254 | |
3392 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
4255 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
|
|
4256 | with the same arguments. Either this method or a suitable start method |
3393 | called at least once. Unlike the C counterpart, an active watcher gets |
4257 | must be called at least once. Unlike the C counterpart, an active watcher |
3394 | automatically stopped and restarted when reconfiguring it with this |
4258 | gets automatically stopped and restarted when reconfiguring it with this |
3395 | method. |
4259 | method. |
|
|
4260 | |
|
|
4261 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4262 | clashing with the C<set (loop)> method. |
3396 | |
4263 | |
3397 | =item w->start () |
4264 | =item w->start () |
3398 | |
4265 | |
3399 | Starts the watcher. Note that there is no C<loop> argument, as the |
4266 | Starts the watcher. Note that there is no C<loop> argument, as the |
3400 | constructor already stores the event loop. |
4267 | constructor already stores the event loop. |
3401 | |
4268 | |
|
|
4269 | =item w->start ([arguments]) |
|
|
4270 | |
|
|
4271 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4272 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4273 | the configure C<set> method of the watcher. |
|
|
4274 | |
3402 | =item w->stop () |
4275 | =item w->stop () |
3403 | |
4276 | |
3404 | Stops the watcher if it is active. Again, no C<loop> argument. |
4277 | Stops the watcher if it is active. Again, no C<loop> argument. |
3405 | |
4278 | |
3406 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4279 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3418 | |
4291 | |
3419 | =back |
4292 | =back |
3420 | |
4293 | |
3421 | =back |
4294 | =back |
3422 | |
4295 | |
3423 | Example: Define a class with an IO and idle watcher, start one of them in |
4296 | Example: Define a class with two I/O and idle watchers, start the I/O |
3424 | the constructor. |
4297 | watchers in the constructor. |
3425 | |
4298 | |
3426 | class myclass |
4299 | class myclass |
3427 | { |
4300 | { |
3428 | ev::io io ; void io_cb (ev::io &w, int revents); |
4301 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4302 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3429 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4303 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3430 | |
4304 | |
3431 | myclass (int fd) |
4305 | myclass (int fd) |
3432 | { |
4306 | { |
3433 | io .set <myclass, &myclass::io_cb > (this); |
4307 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4308 | io2 .set <myclass, &myclass::io2_cb > (this); |
3434 | idle.set <myclass, &myclass::idle_cb> (this); |
4309 | idle.set <myclass, &myclass::idle_cb> (this); |
3435 | |
4310 | |
3436 | io.start (fd, ev::READ); |
4311 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4312 | io.start (); // start it whenever convenient |
|
|
4313 | |
|
|
4314 | io2.start (fd, ev::READ); // set + start in one call |
3437 | } |
4315 | } |
3438 | }; |
4316 | }; |
3439 | |
4317 | |
3440 | |
4318 | |
3441 | =head1 OTHER LANGUAGE BINDINGS |
4319 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3480 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4358 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3481 | |
4359 | |
3482 | =item D |
4360 | =item D |
3483 | |
4361 | |
3484 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4362 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3485 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4363 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3486 | |
4364 | |
3487 | =item Ocaml |
4365 | =item Ocaml |
3488 | |
4366 | |
3489 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4367 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3490 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4368 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3493 | |
4371 | |
3494 | Brian Maher has written a partial interface to libev for lua (at the |
4372 | Brian Maher has written a partial interface to libev for lua (at the |
3495 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4373 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3496 | L<http://github.com/brimworks/lua-ev>. |
4374 | L<http://github.com/brimworks/lua-ev>. |
3497 | |
4375 | |
|
|
4376 | =item Javascript |
|
|
4377 | |
|
|
4378 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4379 | |
|
|
4380 | =item Others |
|
|
4381 | |
|
|
4382 | There are others, and I stopped counting. |
|
|
4383 | |
3498 | =back |
4384 | =back |
3499 | |
4385 | |
3500 | |
4386 | |
3501 | =head1 MACRO MAGIC |
4387 | =head1 MACRO MAGIC |
3502 | |
4388 | |
… | |
… | |
3515 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4401 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3516 | C<EV_A_> is used when other arguments are following. Example: |
4402 | C<EV_A_> is used when other arguments are following. Example: |
3517 | |
4403 | |
3518 | ev_unref (EV_A); |
4404 | ev_unref (EV_A); |
3519 | ev_timer_add (EV_A_ watcher); |
4405 | ev_timer_add (EV_A_ watcher); |
3520 | ev_loop (EV_A_ 0); |
4406 | ev_run (EV_A_ 0); |
3521 | |
4407 | |
3522 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4408 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3523 | which is often provided by the following macro. |
4409 | which is often provided by the following macro. |
3524 | |
4410 | |
3525 | =item C<EV_P>, C<EV_P_> |
4411 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3538 | suitable for use with C<EV_A>. |
4424 | suitable for use with C<EV_A>. |
3539 | |
4425 | |
3540 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4426 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3541 | |
4427 | |
3542 | Similar to the other two macros, this gives you the value of the default |
4428 | Similar to the other two macros, this gives you the value of the default |
3543 | loop, if multiple loops are supported ("ev loop default"). |
4429 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4430 | will be initialised if it isn't already initialised. |
|
|
4431 | |
|
|
4432 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4433 | to initialise the loop somewhere. |
3544 | |
4434 | |
3545 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4435 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3546 | |
4436 | |
3547 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4437 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3548 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4438 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3565 | } |
4455 | } |
3566 | |
4456 | |
3567 | ev_check check; |
4457 | ev_check check; |
3568 | ev_check_init (&check, check_cb); |
4458 | ev_check_init (&check, check_cb); |
3569 | ev_check_start (EV_DEFAULT_ &check); |
4459 | ev_check_start (EV_DEFAULT_ &check); |
3570 | ev_loop (EV_DEFAULT_ 0); |
4460 | ev_run (EV_DEFAULT_ 0); |
3571 | |
4461 | |
3572 | =head1 EMBEDDING |
4462 | =head1 EMBEDDING |
3573 | |
4463 | |
3574 | Libev can (and often is) directly embedded into host |
4464 | Libev can (and often is) directly embedded into host |
3575 | applications. Examples of applications that embed it include the Deliantra |
4465 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3615 | ev_vars.h |
4505 | ev_vars.h |
3616 | ev_wrap.h |
4506 | ev_wrap.h |
3617 | |
4507 | |
3618 | ev_win32.c required on win32 platforms only |
4508 | ev_win32.c required on win32 platforms only |
3619 | |
4509 | |
3620 | ev_select.c only when select backend is enabled (which is enabled by default) |
4510 | ev_select.c only when select backend is enabled |
3621 | ev_poll.c only when poll backend is enabled (disabled by default) |
4511 | ev_poll.c only when poll backend is enabled |
3622 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4512 | ev_epoll.c only when the epoll backend is enabled |
|
|
4513 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4514 | ev_iouring.c only when the linux io_uring backend is enabled |
3623 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4515 | ev_kqueue.c only when the kqueue backend is enabled |
3624 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4516 | ev_port.c only when the solaris port backend is enabled |
3625 | |
4517 | |
3626 | F<ev.c> includes the backend files directly when enabled, so you only need |
4518 | F<ev.c> includes the backend files directly when enabled, so you only need |
3627 | to compile this single file. |
4519 | to compile this single file. |
3628 | |
4520 | |
3629 | =head3 LIBEVENT COMPATIBILITY API |
4521 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
3660 | define before including (or compiling) any of its files. The default in |
4552 | define before including (or compiling) any of its files. The default in |
3661 | the absence of autoconf is documented for every option. |
4553 | the absence of autoconf is documented for every option. |
3662 | |
4554 | |
3663 | Symbols marked with "(h)" do not change the ABI, and can have different |
4555 | Symbols marked with "(h)" do not change the ABI, and can have different |
3664 | values when compiling libev vs. including F<ev.h>, so it is permissible |
4556 | values when compiling libev vs. including F<ev.h>, so it is permissible |
3665 | to redefine them before including F<ev.h> without breakign compatibility |
4557 | to redefine them before including F<ev.h> without breaking compatibility |
3666 | to a compiled library. All other symbols change the ABI, which means all |
4558 | to a compiled library. All other symbols change the ABI, which means all |
3667 | users of libev and the libev code itself must be compiled with compatible |
4559 | users of libev and the libev code itself must be compiled with compatible |
3668 | settings. |
4560 | settings. |
3669 | |
4561 | |
3670 | =over 4 |
4562 | =over 4 |
|
|
4563 | |
|
|
4564 | =item EV_COMPAT3 (h) |
|
|
4565 | |
|
|
4566 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4567 | release of libev comes with wrappers for the functions and symbols that |
|
|
4568 | have been renamed between libev version 3 and 4. |
|
|
4569 | |
|
|
4570 | You can disable these wrappers (to test compatibility with future |
|
|
4571 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4572 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4573 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4574 | typedef in that case. |
|
|
4575 | |
|
|
4576 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4577 | and in some even more future version the compatibility code will be |
|
|
4578 | removed completely. |
3671 | |
4579 | |
3672 | =item EV_STANDALONE (h) |
4580 | =item EV_STANDALONE (h) |
3673 | |
4581 | |
3674 | Must always be C<1> if you do not use autoconf configuration, which |
4582 | Must always be C<1> if you do not use autoconf configuration, which |
3675 | keeps libev from including F<config.h>, and it also defines dummy |
4583 | keeps libev from including F<config.h>, and it also defines dummy |
… | |
… | |
3677 | supported). It will also not define any of the structs usually found in |
4585 | supported). It will also not define any of the structs usually found in |
3678 | F<event.h> that are not directly supported by the libev core alone. |
4586 | F<event.h> that are not directly supported by the libev core alone. |
3679 | |
4587 | |
3680 | In standalone mode, libev will still try to automatically deduce the |
4588 | In standalone mode, libev will still try to automatically deduce the |
3681 | configuration, but has to be more conservative. |
4589 | configuration, but has to be more conservative. |
|
|
4590 | |
|
|
4591 | =item EV_USE_FLOOR |
|
|
4592 | |
|
|
4593 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4594 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4595 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4596 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4597 | function is not available will fail, so the safe default is to not enable |
|
|
4598 | this. |
3682 | |
4599 | |
3683 | =item EV_USE_MONOTONIC |
4600 | =item EV_USE_MONOTONIC |
3684 | |
4601 | |
3685 | If defined to be C<1>, libev will try to detect the availability of the |
4602 | If defined to be C<1>, libev will try to detect the availability of the |
3686 | monotonic clock option at both compile time and runtime. Otherwise no |
4603 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3723 | available and will probe for kernel support at runtime. This will improve |
4640 | available and will probe for kernel support at runtime. This will improve |
3724 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4641 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
3725 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4642 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
3726 | 2.7 or newer, otherwise disabled. |
4643 | 2.7 or newer, otherwise disabled. |
3727 | |
4644 | |
|
|
4645 | =item EV_USE_SIGNALFD |
|
|
4646 | |
|
|
4647 | If defined to be C<1>, then libev will assume that C<signalfd ()> is |
|
|
4648 | available and will probe for kernel support at runtime. This enables |
|
|
4649 | the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If |
|
|
4650 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4651 | 2.7 or newer, otherwise disabled. |
|
|
4652 | |
|
|
4653 | =item EV_USE_TIMERFD |
|
|
4654 | |
|
|
4655 | If defined to be C<1>, then libev will assume that C<timerfd ()> is |
|
|
4656 | available and will probe for kernel support at runtime. This allows |
|
|
4657 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4658 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4659 | C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled. |
|
|
4660 | |
|
|
4661 | =item EV_USE_EVENTFD |
|
|
4662 | |
|
|
4663 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4664 | available and will probe for kernel support at runtime. This will improve |
|
|
4665 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4666 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4667 | 2.7 or newer, otherwise disabled. |
|
|
4668 | |
3728 | =item EV_USE_SELECT |
4669 | =item EV_USE_SELECT |
3729 | |
4670 | |
3730 | If undefined or defined to be C<1>, libev will compile in support for the |
4671 | If undefined or defined to be C<1>, libev will compile in support for the |
3731 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4672 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
3732 | other method takes over, select will be it. Otherwise the select backend |
4673 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
3772 | If programs implement their own fd to handle mapping on win32, then this |
4713 | If programs implement their own fd to handle mapping on win32, then this |
3773 | macro can be used to override the C<close> function, useful to unregister |
4714 | macro can be used to override the C<close> function, useful to unregister |
3774 | file descriptors again. Note that the replacement function has to close |
4715 | file descriptors again. Note that the replacement function has to close |
3775 | the underlying OS handle. |
4716 | the underlying OS handle. |
3776 | |
4717 | |
|
|
4718 | =item EV_USE_WSASOCKET |
|
|
4719 | |
|
|
4720 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4721 | communication socket, which works better in some environments. Otherwise, |
|
|
4722 | the normal C<socket> function will be used, which works better in other |
|
|
4723 | environments. |
|
|
4724 | |
3777 | =item EV_USE_POLL |
4725 | =item EV_USE_POLL |
3778 | |
4726 | |
3779 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4727 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3780 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4728 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3781 | takes precedence over select. |
4729 | takes precedence over select. |
… | |
… | |
3785 | If defined to be C<1>, libev will compile in support for the Linux |
4733 | If defined to be C<1>, libev will compile in support for the Linux |
3786 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4734 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3787 | otherwise another method will be used as fallback. This is the preferred |
4735 | otherwise another method will be used as fallback. This is the preferred |
3788 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4736 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
3789 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4737 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4738 | |
|
|
4739 | =item EV_USE_LINUXAIO |
|
|
4740 | |
|
|
4741 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4742 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4743 | enabled on linux, otherwise disabled. |
|
|
4744 | |
|
|
4745 | =item EV_USE_IOURING |
|
|
4746 | |
|
|
4747 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4748 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
|
|
4749 | current limitations it has to be requested explicitly. If undefined, it |
|
|
4750 | will be enabled on linux, otherwise disabled. |
3790 | |
4751 | |
3791 | =item EV_USE_KQUEUE |
4752 | =item EV_USE_KQUEUE |
3792 | |
4753 | |
3793 | If defined to be C<1>, libev will compile in support for the BSD style |
4754 | If defined to be C<1>, libev will compile in support for the BSD style |
3794 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4755 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
3816 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4777 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3817 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4778 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3818 | be detected at runtime. If undefined, it will be enabled if the headers |
4779 | be detected at runtime. If undefined, it will be enabled if the headers |
3819 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4780 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3820 | |
4781 | |
|
|
4782 | =item EV_NO_SMP |
|
|
4783 | |
|
|
4784 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4785 | between threads, that is, threads can be used, but threads never run on |
|
|
4786 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4787 | and makes libev faster. |
|
|
4788 | |
|
|
4789 | =item EV_NO_THREADS |
|
|
4790 | |
|
|
4791 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4792 | different threads (that includes signal handlers), which is a stronger |
|
|
4793 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4794 | libev faster. |
|
|
4795 | |
3821 | =item EV_ATOMIC_T |
4796 | =item EV_ATOMIC_T |
3822 | |
4797 | |
3823 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4798 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3824 | access is atomic with respect to other threads or signal contexts. No such |
4799 | access is atomic with respect to other threads or signal contexts. No |
3825 | type is easily found in the C language, so you can provide your own type |
4800 | such type is easily found in the C language, so you can provide your own |
3826 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4801 | type that you know is safe for your purposes. It is used both for signal |
3827 | as well as for signal and thread safety in C<ev_async> watchers. |
4802 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4803 | watchers. |
3828 | |
4804 | |
3829 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4805 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3830 | (from F<signal.h>), which is usually good enough on most platforms. |
4806 | (from F<signal.h>), which is usually good enough on most platforms. |
3831 | |
4807 | |
3832 | =item EV_H (h) |
4808 | =item EV_H (h) |
… | |
… | |
3859 | will have the C<struct ev_loop *> as first argument, and you can create |
4835 | will have the C<struct ev_loop *> as first argument, and you can create |
3860 | additional independent event loops. Otherwise there will be no support |
4836 | additional independent event loops. Otherwise there will be no support |
3861 | for multiple event loops and there is no first event loop pointer |
4837 | for multiple event loops and there is no first event loop pointer |
3862 | argument. Instead, all functions act on the single default loop. |
4838 | argument. Instead, all functions act on the single default loop. |
3863 | |
4839 | |
|
|
4840 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4841 | default loop when multiplicity is switched off - you always have to |
|
|
4842 | initialise the loop manually in this case. |
|
|
4843 | |
3864 | =item EV_MINPRI |
4844 | =item EV_MINPRI |
3865 | |
4845 | |
3866 | =item EV_MAXPRI |
4846 | =item EV_MAXPRI |
3867 | |
4847 | |
3868 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4848 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3882 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
4862 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
3883 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
4863 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3884 | |
4864 | |
3885 | If undefined or defined to be C<1> (and the platform supports it), then |
4865 | If undefined or defined to be C<1> (and the platform supports it), then |
3886 | the respective watcher type is supported. If defined to be C<0>, then it |
4866 | the respective watcher type is supported. If defined to be C<0>, then it |
3887 | is not. Disabling watcher types mainly saves codesize. |
4867 | is not. Disabling watcher types mainly saves code size. |
3888 | |
4868 | |
3889 | =item EV_FEATURES |
4869 | =item EV_FEATURES |
3890 | |
4870 | |
3891 | If you need to shave off some kilobytes of code at the expense of some |
4871 | If you need to shave off some kilobytes of code at the expense of some |
3892 | speed (but with the full API), you can define this symbol to request |
4872 | speed (but with the full API), you can define this symbol to request |
3893 | certain subsets of functionality. The default is to enable all features |
4873 | certain subsets of functionality. The default is to enable all features |
3894 | that can be enabled on the platform. |
4874 | that can be enabled on the platform. |
3895 | |
|
|
3896 | Note that using autoconf will usually override most of the features, so |
|
|
3897 | using this symbol makes sense mostly when embedding libev. |
|
|
3898 | |
4875 | |
3899 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
4876 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3900 | with some broad features you want) and then selectively re-enable |
4877 | with some broad features you want) and then selectively re-enable |
3901 | additional parts you want, for example if you want everything minimal, |
4878 | additional parts you want, for example if you want everything minimal, |
3902 | but multiple event loop support, async and child watchers and the poll |
4879 | but multiple event loop support, async and child watchers and the poll |
… | |
… | |
3907 | #define EV_USE_POLL 1 |
4884 | #define EV_USE_POLL 1 |
3908 | #define EV_CHILD_ENABLE 1 |
4885 | #define EV_CHILD_ENABLE 1 |
3909 | #define EV_ASYNC_ENABLE 1 |
4886 | #define EV_ASYNC_ENABLE 1 |
3910 | |
4887 | |
3911 | The actual value is a bitset, it can be a combination of the following |
4888 | The actual value is a bitset, it can be a combination of the following |
3912 | values: |
4889 | values (by default, all of these are enabled): |
3913 | |
4890 | |
3914 | =over 4 |
4891 | =over 4 |
3915 | |
4892 | |
3916 | =item C<1> - faster/larger code |
4893 | =item C<1> - faster/larger code |
3917 | |
4894 | |
3918 | Use larger code to speed up some operations. |
4895 | Use larger code to speed up some operations. |
3919 | |
4896 | |
3920 | Currently this is used to override some inlining decisions (enlarging the roughly |
4897 | Currently this is used to override some inlining decisions (enlarging the |
3921 | 30% code size on amd64. |
4898 | code size by roughly 30% on amd64). |
3922 | |
4899 | |
3923 | When optimising for size, use of compiler flags such as C<-Os> with |
4900 | When optimising for size, use of compiler flags such as C<-Os> with |
3924 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4901 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
3925 | assertions. |
4902 | assertions. |
3926 | |
4903 | |
|
|
4904 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4905 | (e.g. gcc with C<-Os>). |
|
|
4906 | |
3927 | =item C<2> - faster/larger data structures |
4907 | =item C<2> - faster/larger data structures |
3928 | |
4908 | |
3929 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4909 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
3930 | hash table sizes and so on. This will usually further increase codesize |
4910 | hash table sizes and so on. This will usually further increase code size |
3931 | and can additionally have an effect on the size of data structures at |
4911 | and can additionally have an effect on the size of data structures at |
3932 | runtime. |
4912 | runtime. |
3933 | |
4913 | |
|
|
4914 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4915 | (e.g. gcc with C<-Os>). |
|
|
4916 | |
3934 | =item C<4> - full API configuration |
4917 | =item C<4> - full API configuration |
3935 | |
4918 | |
3936 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4919 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
3937 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4920 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
3938 | |
4921 | |
|
|
4922 | =item C<8> - full API |
|
|
4923 | |
3939 | It also enables a lot of the "lesser used" core API functions. See C<ev.h> |
4924 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
3940 | for details on which parts of the API are still available without this |
4925 | details on which parts of the API are still available without this |
3941 | feature, and do not complain if this subset changes over time. |
4926 | feature, and do not complain if this subset changes over time. |
3942 | |
4927 | |
3943 | =item C<8> - enable all optional watcher types |
4928 | =item C<16> - enable all optional watcher types |
3944 | |
4929 | |
3945 | Enables all optional watcher types. If you want to selectively enable |
4930 | Enables all optional watcher types. If you want to selectively enable |
3946 | only some watcher types other than I/O and timers (e.g. prepare, |
4931 | only some watcher types other than I/O and timers (e.g. prepare, |
3947 | embed, async, child...) you can enable them manually by defining |
4932 | embed, async, child...) you can enable them manually by defining |
3948 | C<EV_watchertype_ENABLE> to C<1> instead. |
4933 | C<EV_watchertype_ENABLE> to C<1> instead. |
3949 | |
4934 | |
3950 | =item C<16> - enable all backends |
4935 | =item C<32> - enable all backends |
3951 | |
4936 | |
3952 | This enables all backends - without this feature, you need to enable at |
4937 | This enables all backends - without this feature, you need to enable at |
3953 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
4938 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
3954 | |
4939 | |
3955 | =item C<32> - enable OS-specific "helper" APIs |
4940 | =item C<64> - enable OS-specific "helper" APIs |
3956 | |
4941 | |
3957 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
4942 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
3958 | default. |
4943 | default. |
3959 | |
4944 | |
3960 | =back |
4945 | =back |
3961 | |
4946 | |
3962 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
4947 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
3963 | reduces the compiled size of libev from 24.7Kb to 6.5Kb on my GNU/Linux |
4948 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
3964 | amd64 system, while still giving you I/O watchers, timers and monotonic |
4949 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
3965 | clock support. |
4950 | watchers, timers and monotonic clock support. |
3966 | |
4951 | |
3967 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4952 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
3968 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4953 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
3969 | your program might be left out as well - a binary starting a timer and an |
4954 | your program might be left out as well - a binary starting a timer and an |
3970 | I/O watcher then might come out at only 5Kb. |
4955 | I/O watcher then might come out at only 5Kb. |
3971 | |
4956 | |
|
|
4957 | =item EV_API_STATIC |
|
|
4958 | |
|
|
4959 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4960 | will have static linkage. This means that libev will not export any |
|
|
4961 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4962 | when you embed libev, only want to use libev functions in a single file, |
|
|
4963 | and do not want its identifiers to be visible. |
|
|
4964 | |
|
|
4965 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4966 | wants to use libev. |
|
|
4967 | |
|
|
4968 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4969 | doesn't support the required declaration syntax. |
|
|
4970 | |
3972 | =item EV_AVOID_STDIO |
4971 | =item EV_AVOID_STDIO |
3973 | |
4972 | |
3974 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4973 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
3975 | functions (printf, scanf, perror etc.). This will increase the codesize |
4974 | functions (printf, scanf, perror etc.). This will increase the code size |
3976 | somewhat, but if your program doesn't otherwise depend on stdio and your |
4975 | somewhat, but if your program doesn't otherwise depend on stdio and your |
3977 | libc allows it, this avoids linking in the stdio library which is quite |
4976 | libc allows it, this avoids linking in the stdio library which is quite |
3978 | big. |
4977 | big. |
3979 | |
4978 | |
3980 | Note that error messages might become less precise when this option is |
4979 | Note that error messages might become less precise when this option is |
… | |
… | |
3984 | |
4983 | |
3985 | The highest supported signal number, +1 (or, the number of |
4984 | The highest supported signal number, +1 (or, the number of |
3986 | signals): Normally, libev tries to deduce the maximum number of signals |
4985 | signals): Normally, libev tries to deduce the maximum number of signals |
3987 | automatically, but sometimes this fails, in which case it can be |
4986 | automatically, but sometimes this fails, in which case it can be |
3988 | specified. Also, using a lower number than detected (C<32> should be |
4987 | specified. Also, using a lower number than detected (C<32> should be |
3989 | good for about any system in existance) can save some memory, as libev |
4988 | good for about any system in existence) can save some memory, as libev |
3990 | statically allocates some 12-24 bytes per signal number. |
4989 | statically allocates some 12-24 bytes per signal number. |
3991 | |
4990 | |
3992 | =item EV_PID_HASHSIZE |
4991 | =item EV_PID_HASHSIZE |
3993 | |
4992 | |
3994 | C<ev_child> watchers use a small hash table to distribute workload by |
4993 | C<ev_child> watchers use a small hash table to distribute workload by |
… | |
… | |
4026 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5025 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4027 | will be C<0>. |
5026 | will be C<0>. |
4028 | |
5027 | |
4029 | =item EV_VERIFY |
5028 | =item EV_VERIFY |
4030 | |
5029 | |
4031 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
5030 | Controls how much internal verification (see C<ev_verify ()>) will |
4032 | be done: If set to C<0>, no internal verification code will be compiled |
5031 | be done: If set to C<0>, no internal verification code will be compiled |
4033 | in. If set to C<1>, then verification code will be compiled in, but not |
5032 | in. If set to C<1>, then verification code will be compiled in, but not |
4034 | called. If set to C<2>, then the internal verification code will be |
5033 | called. If set to C<2>, then the internal verification code will be |
4035 | called once per loop, which can slow down libev. If set to C<3>, then the |
5034 | called once per loop, which can slow down libev. If set to C<3>, then the |
4036 | verification code will be called very frequently, which will slow down |
5035 | verification code will be called very frequently, which will slow down |
4037 | libev considerably. |
5036 | libev considerably. |
4038 | |
5037 | |
|
|
5038 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
5039 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
|
|
5040 | |
4039 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5041 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4040 | will be C<0>. |
5042 | will be C<0>. |
4041 | |
5043 | |
4042 | =item EV_COMMON |
5044 | =item EV_COMMON |
4043 | |
5045 | |
4044 | By default, all watchers have a C<void *data> member. By redefining |
5046 | By default, all watchers have a C<void *data> member. By redefining |
4045 | this macro to a something else you can include more and other types of |
5047 | this macro to something else you can include more and other types of |
4046 | members. You have to define it each time you include one of the files, |
5048 | members. You have to define it each time you include one of the files, |
4047 | though, and it must be identical each time. |
5049 | though, and it must be identical each time. |
4048 | |
5050 | |
4049 | For example, the perl EV module uses something like this: |
5051 | For example, the perl EV module uses something like this: |
4050 | |
5052 | |
… | |
… | |
4103 | file. |
5105 | file. |
4104 | |
5106 | |
4105 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
5107 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4106 | that everybody includes and which overrides some configure choices: |
5108 | that everybody includes and which overrides some configure choices: |
4107 | |
5109 | |
4108 | #define EV_FEATURES 0 |
5110 | #define EV_FEATURES 8 |
4109 | #define EV_USE_SELECT 1 |
5111 | #define EV_USE_SELECT 1 |
|
|
5112 | #define EV_PREPARE_ENABLE 1 |
|
|
5113 | #define EV_IDLE_ENABLE 1 |
|
|
5114 | #define EV_SIGNAL_ENABLE 1 |
|
|
5115 | #define EV_CHILD_ENABLE 1 |
|
|
5116 | #define EV_USE_STDEXCEPT 0 |
4110 | #define EV_CONFIG_H <config.h> |
5117 | #define EV_CONFIG_H <config.h> |
4111 | |
5118 | |
4112 | #include "ev++.h" |
5119 | #include "ev++.h" |
4113 | |
5120 | |
4114 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
5121 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4115 | |
5122 | |
4116 | #include "ev_cpp.h" |
5123 | #include "ev_cpp.h" |
4117 | #include "ev.c" |
5124 | #include "ev.c" |
4118 | |
5125 | |
4119 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
5126 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4120 | |
5127 | |
4121 | =head2 THREADS AND COROUTINES |
5128 | =head2 THREADS AND COROUTINES |
4122 | |
5129 | |
4123 | =head3 THREADS |
5130 | =head3 THREADS |
4124 | |
5131 | |
… | |
… | |
4175 | default loop and triggering an C<ev_async> watcher from the default loop |
5182 | default loop and triggering an C<ev_async> watcher from the default loop |
4176 | watcher callback into the event loop interested in the signal. |
5183 | watcher callback into the event loop interested in the signal. |
4177 | |
5184 | |
4178 | =back |
5185 | =back |
4179 | |
5186 | |
4180 | =head4 THREAD LOCKING EXAMPLE |
5187 | See also L</THREAD LOCKING EXAMPLE>. |
4181 | |
|
|
4182 | Here is a fictitious example of how to run an event loop in a different |
|
|
4183 | thread than where callbacks are being invoked and watchers are |
|
|
4184 | created/added/removed. |
|
|
4185 | |
|
|
4186 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4187 | which uses exactly this technique (which is suited for many high-level |
|
|
4188 | languages). |
|
|
4189 | |
|
|
4190 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4191 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4192 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4193 | |
|
|
4194 | First, you need to associate some data with the event loop: |
|
|
4195 | |
|
|
4196 | typedef struct { |
|
|
4197 | mutex_t lock; /* global loop lock */ |
|
|
4198 | ev_async async_w; |
|
|
4199 | thread_t tid; |
|
|
4200 | cond_t invoke_cv; |
|
|
4201 | } userdata; |
|
|
4202 | |
|
|
4203 | void prepare_loop (EV_P) |
|
|
4204 | { |
|
|
4205 | // for simplicity, we use a static userdata struct. |
|
|
4206 | static userdata u; |
|
|
4207 | |
|
|
4208 | ev_async_init (&u->async_w, async_cb); |
|
|
4209 | ev_async_start (EV_A_ &u->async_w); |
|
|
4210 | |
|
|
4211 | pthread_mutex_init (&u->lock, 0); |
|
|
4212 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4213 | |
|
|
4214 | // now associate this with the loop |
|
|
4215 | ev_set_userdata (EV_A_ u); |
|
|
4216 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4217 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4218 | |
|
|
4219 | // then create the thread running ev_loop |
|
|
4220 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4221 | } |
|
|
4222 | |
|
|
4223 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4224 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4225 | that might have been added: |
|
|
4226 | |
|
|
4227 | static void |
|
|
4228 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4229 | { |
|
|
4230 | // just used for the side effects |
|
|
4231 | } |
|
|
4232 | |
|
|
4233 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4234 | protecting the loop data, respectively. |
|
|
4235 | |
|
|
4236 | static void |
|
|
4237 | l_release (EV_P) |
|
|
4238 | { |
|
|
4239 | userdata *u = ev_userdata (EV_A); |
|
|
4240 | pthread_mutex_unlock (&u->lock); |
|
|
4241 | } |
|
|
4242 | |
|
|
4243 | static void |
|
|
4244 | l_acquire (EV_P) |
|
|
4245 | { |
|
|
4246 | userdata *u = ev_userdata (EV_A); |
|
|
4247 | pthread_mutex_lock (&u->lock); |
|
|
4248 | } |
|
|
4249 | |
|
|
4250 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4251 | into C<ev_loop>: |
|
|
4252 | |
|
|
4253 | void * |
|
|
4254 | l_run (void *thr_arg) |
|
|
4255 | { |
|
|
4256 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4257 | |
|
|
4258 | l_acquire (EV_A); |
|
|
4259 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4260 | ev_loop (EV_A_ 0); |
|
|
4261 | l_release (EV_A); |
|
|
4262 | |
|
|
4263 | return 0; |
|
|
4264 | } |
|
|
4265 | |
|
|
4266 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4267 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4268 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4269 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4270 | and b) skipping inter-thread-communication when there are no pending |
|
|
4271 | watchers is very beneficial): |
|
|
4272 | |
|
|
4273 | static void |
|
|
4274 | l_invoke (EV_P) |
|
|
4275 | { |
|
|
4276 | userdata *u = ev_userdata (EV_A); |
|
|
4277 | |
|
|
4278 | while (ev_pending_count (EV_A)) |
|
|
4279 | { |
|
|
4280 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4281 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4282 | } |
|
|
4283 | } |
|
|
4284 | |
|
|
4285 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4286 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4287 | thread to continue: |
|
|
4288 | |
|
|
4289 | static void |
|
|
4290 | real_invoke_pending (EV_P) |
|
|
4291 | { |
|
|
4292 | userdata *u = ev_userdata (EV_A); |
|
|
4293 | |
|
|
4294 | pthread_mutex_lock (&u->lock); |
|
|
4295 | ev_invoke_pending (EV_A); |
|
|
4296 | pthread_cond_signal (&u->invoke_cv); |
|
|
4297 | pthread_mutex_unlock (&u->lock); |
|
|
4298 | } |
|
|
4299 | |
|
|
4300 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4301 | event loop, you will now have to lock: |
|
|
4302 | |
|
|
4303 | ev_timer timeout_watcher; |
|
|
4304 | userdata *u = ev_userdata (EV_A); |
|
|
4305 | |
|
|
4306 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4307 | |
|
|
4308 | pthread_mutex_lock (&u->lock); |
|
|
4309 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4310 | ev_async_send (EV_A_ &u->async_w); |
|
|
4311 | pthread_mutex_unlock (&u->lock); |
|
|
4312 | |
|
|
4313 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4314 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4315 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4316 | watchers in the next event loop iteration. |
|
|
4317 | |
5188 | |
4318 | =head3 COROUTINES |
5189 | =head3 COROUTINES |
4319 | |
5190 | |
4320 | Libev is very accommodating to coroutines ("cooperative threads"): |
5191 | Libev is very accommodating to coroutines ("cooperative threads"): |
4321 | libev fully supports nesting calls to its functions from different |
5192 | libev fully supports nesting calls to its functions from different |
4322 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
5193 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
4323 | different coroutines, and switch freely between both coroutines running |
5194 | different coroutines, and switch freely between both coroutines running |
4324 | the loop, as long as you don't confuse yourself). The only exception is |
5195 | the loop, as long as you don't confuse yourself). The only exception is |
4325 | that you must not do this from C<ev_periodic> reschedule callbacks. |
5196 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4326 | |
5197 | |
4327 | Care has been taken to ensure that libev does not keep local state inside |
5198 | Care has been taken to ensure that libev does not keep local state inside |
4328 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
5199 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
4329 | they do not call any callbacks. |
5200 | they do not call any callbacks. |
4330 | |
5201 | |
4331 | =head2 COMPILER WARNINGS |
5202 | =head2 COMPILER WARNINGS |
4332 | |
5203 | |
4333 | Depending on your compiler and compiler settings, you might get no or a |
5204 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
4344 | maintainable. |
5215 | maintainable. |
4345 | |
5216 | |
4346 | And of course, some compiler warnings are just plain stupid, or simply |
5217 | And of course, some compiler warnings are just plain stupid, or simply |
4347 | wrong (because they don't actually warn about the condition their message |
5218 | wrong (because they don't actually warn about the condition their message |
4348 | seems to warn about). For example, certain older gcc versions had some |
5219 | seems to warn about). For example, certain older gcc versions had some |
4349 | warnings that resulted an extreme number of false positives. These have |
5220 | warnings that resulted in an extreme number of false positives. These have |
4350 | been fixed, but some people still insist on making code warn-free with |
5221 | been fixed, but some people still insist on making code warn-free with |
4351 | such buggy versions. |
5222 | such buggy versions. |
4352 | |
5223 | |
4353 | While libev is written to generate as few warnings as possible, |
5224 | While libev is written to generate as few warnings as possible, |
4354 | "warn-free" code is not a goal, and it is recommended not to build libev |
5225 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
4390 | I suggest using suppression lists. |
5261 | I suggest using suppression lists. |
4391 | |
5262 | |
4392 | |
5263 | |
4393 | =head1 PORTABILITY NOTES |
5264 | =head1 PORTABILITY NOTES |
4394 | |
5265 | |
|
|
5266 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
5267 | |
|
|
5268 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5269 | interfaces but I<disables> them by default. |
|
|
5270 | |
|
|
5271 | That means that libev compiled in the default environment doesn't support |
|
|
5272 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
5273 | |
|
|
5274 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5275 | by enabling the large file API, which makes them incompatible with the |
|
|
5276 | standard libev compiled for their system. |
|
|
5277 | |
|
|
5278 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5279 | suddenly make it incompatible to the default compile time environment, |
|
|
5280 | i.e. all programs not using special compile switches. |
|
|
5281 | |
|
|
5282 | =head2 OS/X AND DARWIN BUGS |
|
|
5283 | |
|
|
5284 | The whole thing is a bug if you ask me - basically any system interface |
|
|
5285 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5286 | OpenGL drivers. |
|
|
5287 | |
|
|
5288 | =head3 C<kqueue> is buggy |
|
|
5289 | |
|
|
5290 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5291 | only sockets, many support pipes. |
|
|
5292 | |
|
|
5293 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5294 | rotten platform, but of course you can still ask for it when creating a |
|
|
5295 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5296 | probably going to work well. |
|
|
5297 | |
|
|
5298 | =head3 C<poll> is buggy |
|
|
5299 | |
|
|
5300 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5301 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5302 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5303 | |
|
|
5304 | Libev tries to work around this by not using C<poll> by default on |
|
|
5305 | this rotten platform, but of course you can still ask for it when creating |
|
|
5306 | a loop. |
|
|
5307 | |
|
|
5308 | =head3 C<select> is buggy |
|
|
5309 | |
|
|
5310 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5311 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5312 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5313 | you use more. |
|
|
5314 | |
|
|
5315 | There is an undocumented "workaround" for this - defining |
|
|
5316 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5317 | work on OS/X. |
|
|
5318 | |
|
|
5319 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5320 | |
|
|
5321 | =head3 C<errno> reentrancy |
|
|
5322 | |
|
|
5323 | The default compile environment on Solaris is unfortunately so |
|
|
5324 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5325 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5326 | defined by default. A valid, if stupid, implementation choice. |
|
|
5327 | |
|
|
5328 | If you want to use libev in threaded environments you have to make sure |
|
|
5329 | it's compiled with C<_REENTRANT> defined. |
|
|
5330 | |
|
|
5331 | =head3 Event port backend |
|
|
5332 | |
|
|
5333 | The scalable event interface for Solaris is called "event |
|
|
5334 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5335 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5336 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5337 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5338 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5339 | great. |
|
|
5340 | |
|
|
5341 | If you can't get it to work, you can try running the program by setting |
|
|
5342 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5343 | C<select> backends. |
|
|
5344 | |
|
|
5345 | =head2 AIX POLL BUG |
|
|
5346 | |
|
|
5347 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5348 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5349 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5350 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5351 | |
4395 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5352 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5353 | |
|
|
5354 | =head3 General issues |
4396 | |
5355 | |
4397 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5356 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4398 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5357 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4399 | model. Libev still offers limited functionality on this platform in |
5358 | model. Libev still offers limited functionality on this platform in |
4400 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5359 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4401 | descriptors. This only applies when using Win32 natively, not when using |
5360 | descriptors. This only applies when using Win32 natively, not when using |
4402 | e.g. cygwin. |
5361 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5362 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5363 | environment. |
4403 | |
5364 | |
4404 | Lifting these limitations would basically require the full |
5365 | Lifting these limitations would basically require the full |
4405 | re-implementation of the I/O system. If you are into these kinds of |
5366 | re-implementation of the I/O system. If you are into this kind of thing, |
4406 | things, then note that glib does exactly that for you in a very portable |
5367 | then note that glib does exactly that for you in a very portable way (note |
4407 | way (note also that glib is the slowest event library known to man). |
5368 | also that glib is the slowest event library known to man). |
4408 | |
5369 | |
4409 | There is no supported compilation method available on windows except |
5370 | There is no supported compilation method available on windows except |
4410 | embedding it into other applications. |
5371 | embedding it into other applications. |
4411 | |
5372 | |
4412 | Sensible signal handling is officially unsupported by Microsoft - libev |
5373 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4440 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
5401 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4441 | |
5402 | |
4442 | #include "evwrap.h" |
5403 | #include "evwrap.h" |
4443 | #include "ev.c" |
5404 | #include "ev.c" |
4444 | |
5405 | |
4445 | =over 4 |
|
|
4446 | |
|
|
4447 | =item The winsocket select function |
5406 | =head3 The winsocket C<select> function |
4448 | |
5407 | |
4449 | The winsocket C<select> function doesn't follow POSIX in that it |
5408 | The winsocket C<select> function doesn't follow POSIX in that it |
4450 | requires socket I<handles> and not socket I<file descriptors> (it is |
5409 | requires socket I<handles> and not socket I<file descriptors> (it is |
4451 | also extremely buggy). This makes select very inefficient, and also |
5410 | also extremely buggy). This makes select very inefficient, and also |
4452 | requires a mapping from file descriptors to socket handles (the Microsoft |
5411 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4461 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5420 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4462 | |
5421 | |
4463 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5422 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4464 | complexity in the O(n²) range when using win32. |
5423 | complexity in the O(n²) range when using win32. |
4465 | |
5424 | |
4466 | =item Limited number of file descriptors |
5425 | =head3 Limited number of file descriptors |
4467 | |
5426 | |
4468 | Windows has numerous arbitrary (and low) limits on things. |
5427 | Windows has numerous arbitrary (and low) limits on things. |
4469 | |
5428 | |
4470 | Early versions of winsocket's select only supported waiting for a maximum |
5429 | Early versions of winsocket's select only supported waiting for a maximum |
4471 | of C<64> handles (probably owning to the fact that all windows kernels |
5430 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4486 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
5445 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4487 | (depending on windows version and/or the phase of the moon). To get more, |
5446 | (depending on windows version and/or the phase of the moon). To get more, |
4488 | you need to wrap all I/O functions and provide your own fd management, but |
5447 | you need to wrap all I/O functions and provide your own fd management, but |
4489 | the cost of calling select (O(n²)) will likely make this unworkable. |
5448 | the cost of calling select (O(n²)) will likely make this unworkable. |
4490 | |
5449 | |
4491 | =back |
|
|
4492 | |
|
|
4493 | =head2 PORTABILITY REQUIREMENTS |
5450 | =head2 PORTABILITY REQUIREMENTS |
4494 | |
5451 | |
4495 | In addition to a working ISO-C implementation and of course the |
5452 | In addition to a working ISO-C implementation and of course the |
4496 | backend-specific APIs, libev relies on a few additional extensions: |
5453 | backend-specific APIs, libev relies on a few additional extensions: |
4497 | |
5454 | |
… | |
… | |
4503 | Libev assumes not only that all watcher pointers have the same internal |
5460 | Libev assumes not only that all watcher pointers have the same internal |
4504 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5461 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4505 | assumes that the same (machine) code can be used to call any watcher |
5462 | assumes that the same (machine) code can be used to call any watcher |
4506 | callback: The watcher callbacks have different type signatures, but libev |
5463 | callback: The watcher callbacks have different type signatures, but libev |
4507 | calls them using an C<ev_watcher *> internally. |
5464 | calls them using an C<ev_watcher *> internally. |
|
|
5465 | |
|
|
5466 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5467 | |
|
|
5468 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5469 | relies on this setting pointers and integers to null. |
|
|
5470 | |
|
|
5471 | =item pointer accesses must be thread-atomic |
|
|
5472 | |
|
|
5473 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5474 | writable in one piece - this is the case on all current architectures. |
4508 | |
5475 | |
4509 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5476 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4510 | |
5477 | |
4511 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5478 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4512 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5479 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
4521 | thread" or will block signals process-wide, both behaviours would |
5488 | thread" or will block signals process-wide, both behaviours would |
4522 | be compatible with libev. Interaction between C<sigprocmask> and |
5489 | be compatible with libev. Interaction between C<sigprocmask> and |
4523 | C<pthread_sigmask> could complicate things, however. |
5490 | C<pthread_sigmask> could complicate things, however. |
4524 | |
5491 | |
4525 | The most portable way to handle signals is to block signals in all threads |
5492 | The most portable way to handle signals is to block signals in all threads |
4526 | except the initial one, and run the default loop in the initial thread as |
5493 | except the initial one, and run the signal handling loop in the initial |
4527 | well. |
5494 | thread as well. |
4528 | |
5495 | |
4529 | =item C<long> must be large enough for common memory allocation sizes |
5496 | =item C<long> must be large enough for common memory allocation sizes |
4530 | |
5497 | |
4531 | To improve portability and simplify its API, libev uses C<long> internally |
5498 | To improve portability and simplify its API, libev uses C<long> internally |
4532 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5499 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4535 | watchers. |
5502 | watchers. |
4536 | |
5503 | |
4537 | =item C<double> must hold a time value in seconds with enough accuracy |
5504 | =item C<double> must hold a time value in seconds with enough accuracy |
4538 | |
5505 | |
4539 | The type C<double> is used to represent timestamps. It is required to |
5506 | The type C<double> is used to represent timestamps. It is required to |
4540 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5507 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4541 | enough for at least into the year 4000. This requirement is fulfilled by |
5508 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5509 | (the design goal for libev). This requirement is overfulfilled by |
4542 | implementations implementing IEEE 754, which is basically all existing |
5510 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5511 | |
4543 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
5512 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
4544 | 2200. |
5513 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5514 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5515 | something like that, just kidding). |
4545 | |
5516 | |
4546 | =back |
5517 | =back |
4547 | |
5518 | |
4548 | If you know of other additional requirements drop me a note. |
5519 | If you know of other additional requirements drop me a note. |
4549 | |
5520 | |
… | |
… | |
4611 | =item Processing ev_async_send: O(number_of_async_watchers) |
5582 | =item Processing ev_async_send: O(number_of_async_watchers) |
4612 | |
5583 | |
4613 | =item Processing signals: O(max_signal_number) |
5584 | =item Processing signals: O(max_signal_number) |
4614 | |
5585 | |
4615 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5586 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4616 | calls in the current loop iteration. Checking for async and signal events |
5587 | calls in the current loop iteration and the loop is currently |
|
|
5588 | blocked. Checking for async and signal events involves iterating over all |
4617 | involves iterating over all running async watchers or all signal numbers. |
5589 | running async watchers or all signal numbers. |
4618 | |
5590 | |
4619 | =back |
5591 | =back |
4620 | |
5592 | |
4621 | |
5593 | |
|
|
5594 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5595 | |
|
|
5596 | The major version 4 introduced some incompatible changes to the API. |
|
|
5597 | |
|
|
5598 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5599 | for all changes, so most programs should still compile. The compatibility |
|
|
5600 | layer might be removed in later versions of libev, so better update to the |
|
|
5601 | new API early than late. |
|
|
5602 | |
|
|
5603 | =over 4 |
|
|
5604 | |
|
|
5605 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5606 | |
|
|
5607 | The backward compatibility mechanism can be controlled by |
|
|
5608 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5609 | section. |
|
|
5610 | |
|
|
5611 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5612 | |
|
|
5613 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5614 | |
|
|
5615 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5616 | ev_loop_fork (EV_DEFAULT); |
|
|
5617 | |
|
|
5618 | =item function/symbol renames |
|
|
5619 | |
|
|
5620 | A number of functions and symbols have been renamed: |
|
|
5621 | |
|
|
5622 | ev_loop => ev_run |
|
|
5623 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5624 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5625 | |
|
|
5626 | ev_unloop => ev_break |
|
|
5627 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5628 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5629 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5630 | |
|
|
5631 | EV_TIMEOUT => EV_TIMER |
|
|
5632 | |
|
|
5633 | ev_loop_count => ev_iteration |
|
|
5634 | ev_loop_depth => ev_depth |
|
|
5635 | ev_loop_verify => ev_verify |
|
|
5636 | |
|
|
5637 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5638 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5639 | associated constants have been renamed to not collide with the C<struct |
|
|
5640 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5641 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5642 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5643 | typedef. |
|
|
5644 | |
|
|
5645 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5646 | |
|
|
5647 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5648 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5649 | and work, but the library code will of course be larger. |
|
|
5650 | |
|
|
5651 | =back |
|
|
5652 | |
|
|
5653 | |
4622 | =head1 GLOSSARY |
5654 | =head1 GLOSSARY |
4623 | |
5655 | |
4624 | =over 4 |
5656 | =over 4 |
4625 | |
5657 | |
4626 | =item active |
5658 | =item active |
4627 | |
5659 | |
4628 | A watcher is active as long as it has been started (has been attached to |
5660 | A watcher is active as long as it has been started and not yet stopped. |
4629 | an event loop) but not yet stopped (disassociated from the event loop). |
5661 | See L</WATCHER STATES> for details. |
4630 | |
5662 | |
4631 | =item application |
5663 | =item application |
4632 | |
5664 | |
4633 | In this document, an application is whatever is using libev. |
5665 | In this document, an application is whatever is using libev. |
|
|
5666 | |
|
|
5667 | =item backend |
|
|
5668 | |
|
|
5669 | The part of the code dealing with the operating system interfaces. |
4634 | |
5670 | |
4635 | =item callback |
5671 | =item callback |
4636 | |
5672 | |
4637 | The address of a function that is called when some event has been |
5673 | The address of a function that is called when some event has been |
4638 | detected. Callbacks are being passed the event loop, the watcher that |
5674 | detected. Callbacks are being passed the event loop, the watcher that |
4639 | received the event, and the actual event bitset. |
5675 | received the event, and the actual event bitset. |
4640 | |
5676 | |
4641 | =item callback invocation |
5677 | =item callback/watcher invocation |
4642 | |
5678 | |
4643 | The act of calling the callback associated with a watcher. |
5679 | The act of calling the callback associated with a watcher. |
4644 | |
5680 | |
4645 | =item event |
5681 | =item event |
4646 | |
5682 | |
4647 | A change of state of some external event, such as data now being available |
5683 | A change of state of some external event, such as data now being available |
4648 | for reading on a file descriptor, time having passed or simply not having |
5684 | for reading on a file descriptor, time having passed or simply not having |
4649 | any other events happening anymore. |
5685 | any other events happening anymore. |
4650 | |
5686 | |
4651 | In libev, events are represented as single bits (such as C<EV_READ> or |
5687 | In libev, events are represented as single bits (such as C<EV_READ> or |
4652 | C<EV_TIMEOUT>). |
5688 | C<EV_TIMER>). |
4653 | |
5689 | |
4654 | =item event library |
5690 | =item event library |
4655 | |
5691 | |
4656 | A software package implementing an event model and loop. |
5692 | A software package implementing an event model and loop. |
4657 | |
5693 | |
… | |
… | |
4665 | The model used to describe how an event loop handles and processes |
5701 | The model used to describe how an event loop handles and processes |
4666 | watchers and events. |
5702 | watchers and events. |
4667 | |
5703 | |
4668 | =item pending |
5704 | =item pending |
4669 | |
5705 | |
4670 | A watcher is pending as soon as the corresponding event has been detected, |
5706 | A watcher is pending as soon as the corresponding event has been |
4671 | and stops being pending as soon as the watcher will be invoked or its |
5707 | detected. See L</WATCHER STATES> for details. |
4672 | pending status is explicitly cleared by the application. |
|
|
4673 | |
|
|
4674 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4675 | its pending status. |
|
|
4676 | |
5708 | |
4677 | =item real time |
5709 | =item real time |
4678 | |
5710 | |
4679 | The physical time that is observed. It is apparently strictly monotonic :) |
5711 | The physical time that is observed. It is apparently strictly monotonic :) |
4680 | |
5712 | |
4681 | =item wall-clock time |
5713 | =item wall-clock time |
4682 | |
5714 | |
4683 | The time and date as shown on clocks. Unlike real time, it can actually |
5715 | The time and date as shown on clocks. Unlike real time, it can actually |
4684 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5716 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4685 | clock. |
5717 | clock. |
4686 | |
5718 | |
4687 | =item watcher |
5719 | =item watcher |
4688 | |
5720 | |
4689 | A data structure that describes interest in certain events. Watchers need |
5721 | A data structure that describes interest in certain events. Watchers need |
4690 | to be started (attached to an event loop) before they can receive events. |
5722 | to be started (attached to an event loop) before they can receive events. |
4691 | |
5723 | |
4692 | =item watcher invocation |
|
|
4693 | |
|
|
4694 | The act of calling the callback associated with a watcher. |
|
|
4695 | |
|
|
4696 | =back |
5724 | =back |
4697 | |
5725 | |
4698 | =head1 AUTHOR |
5726 | =head1 AUTHOR |
4699 | |
5727 | |
4700 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5728 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5729 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4701 | |
5730 | |