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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_loop's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
52 | |
54 | |
53 | // initialise a timer watcher, then start it |
55 | // initialise a timer watcher, then start it |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_loop (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
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84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
133 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
134 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
135 | throughout libev. |
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136 | |
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137 | =head1 ERROR HANDLING |
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138 | |
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139 | Libev knows three classes of errors: operating system errors, usage errors |
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140 | and internal errors (bugs). |
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141 | |
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142 | When libev catches an operating system error it cannot handle (for example |
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143 | a system call indicating a condition libev cannot fix), it calls the callback |
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144 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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145 | abort. The default is to print a diagnostic message and to call C<abort |
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146 | ()>. |
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147 | |
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148 | When libev detects a usage error such as a negative timer interval, then |
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149 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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150 | so C<NDEBUG> will disable this checking): these are programming errors in |
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151 | the libev caller and need to be fixed there. |
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152 | |
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153 | Libev also has a few internal error-checking C<assert>ions, and also has |
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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. |
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156 | |
121 | |
157 | |
122 | =head1 GLOBAL FUNCTIONS |
158 | =head1 GLOBAL FUNCTIONS |
123 | |
159 | |
124 | These functions can be called anytime, even before initialising the |
160 | These functions can be called anytime, even before initialising the |
125 | library in any way. |
161 | library in any way. |
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134 | |
170 | |
135 | =item ev_sleep (ev_tstamp interval) |
171 | =item ev_sleep (ev_tstamp interval) |
136 | |
172 | |
137 | Sleep for the given interval: The current thread will be blocked until |
173 | Sleep for the given interval: The current thread will be blocked until |
138 | either it is interrupted or the given time interval has passed. Basically |
174 | either it is interrupted or the given time interval has passed. Basically |
139 | this is a subsecond-resolution C<sleep ()>. |
175 | this is a sub-second-resolution C<sleep ()>. |
140 | |
176 | |
141 | =item int ev_version_major () |
177 | =item int ev_version_major () |
142 | |
178 | |
143 | =item int ev_version_minor () |
179 | =item int ev_version_minor () |
144 | |
180 | |
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157 | not a problem. |
193 | not a problem. |
158 | |
194 | |
159 | Example: Make sure we haven't accidentally been linked against the wrong |
195 | Example: Make sure we haven't accidentally been linked against the wrong |
160 | version. |
196 | version. |
161 | |
197 | |
162 | assert (("libev version mismatch", |
198 | assert (("libev version mismatch", |
163 | ev_version_major () == EV_VERSION_MAJOR |
199 | ev_version_major () == EV_VERSION_MAJOR |
164 | && ev_version_minor () >= EV_VERSION_MINOR)); |
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
165 | |
201 | |
166 | =item unsigned int ev_supported_backends () |
202 | =item unsigned int ev_supported_backends () |
167 | |
203 | |
168 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
204 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
169 | value) compiled into this binary of libev (independent of their |
205 | value) compiled into this binary of libev (independent of their |
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171 | a description of the set values. |
207 | a description of the set values. |
172 | |
208 | |
173 | Example: make sure we have the epoll method, because yeah this is cool and |
209 | Example: make sure we have the epoll method, because yeah this is cool and |
174 | a must have and can we have a torrent of it please!!!11 |
210 | a must have and can we have a torrent of it please!!!11 |
175 | |
211 | |
176 | assert (("sorry, no epoll, no sex", |
212 | assert (("sorry, no epoll, no sex", |
177 | ev_supported_backends () & EVBACKEND_EPOLL)); |
213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
178 | |
214 | |
179 | =item unsigned int ev_recommended_backends () |
215 | =item unsigned int ev_recommended_backends () |
180 | |
216 | |
181 | Return the set of all backends compiled into this binary of libev and also |
217 | Return the set of all backends compiled into this binary of libev and also |
182 | recommended for this platform. This set is often smaller than the one |
218 | recommended for this platform. This set is often smaller than the one |
183 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
219 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
184 | most BSDs and will not be autodetected unless you explicitly request it |
220 | most BSDs and will not be auto-detected unless you explicitly request it |
185 | (assuming you know what you are doing). This is the set of backends that |
221 | (assuming you know what you are doing). This is the set of backends that |
186 | libev will probe for if you specify no backends explicitly. |
222 | libev will probe for if you specify no backends explicitly. |
187 | |
223 | |
188 | =item unsigned int ev_embeddable_backends () |
224 | =item unsigned int ev_embeddable_backends () |
189 | |
225 | |
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193 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
194 | recommended ones. |
230 | recommended ones. |
195 | |
231 | |
196 | See the description of C<ev_embed> watchers for more info. |
232 | See the description of C<ev_embed> watchers for more info. |
197 | |
233 | |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
199 | |
235 | |
200 | Sets the allocation function to use (the prototype is similar - the |
236 | Sets the allocation function to use (the prototype is similar - the |
201 | semantics is identical - to the realloc C function). It is used to |
237 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
202 | allocate and free memory (no surprises here). If it returns zero when |
238 | used to allocate and free memory (no surprises here). If it returns zero |
203 | memory needs to be allocated, the library might abort or take some |
239 | when memory needs to be allocated (C<size != 0>), the library might abort |
204 | potentially destructive action. The default is your system realloc |
240 | or take some potentially destructive action. |
205 | function. |
241 | |
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242 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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243 | correct C<realloc> semantics, libev will use a wrapper around the system |
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244 | C<realloc> and C<free> functions by default. |
206 | |
245 | |
207 | You could override this function in high-availability programs to, say, |
246 | You could override this function in high-availability programs to, say, |
208 | free some memory if it cannot allocate memory, to use a special allocator, |
247 | free some memory if it cannot allocate memory, to use a special allocator, |
209 | or even to sleep a while and retry until some memory is available. |
248 | or even to sleep a while and retry until some memory is available. |
210 | |
249 | |
211 | Example: Replace the libev allocator with one that waits a bit and then |
250 | Example: Replace the libev allocator with one that waits a bit and then |
212 | retries). |
251 | retries (example requires a standards-compliant C<realloc>). |
213 | |
252 | |
214 | static void * |
253 | static void * |
215 | persistent_realloc (void *ptr, size_t size) |
254 | persistent_realloc (void *ptr, size_t size) |
216 | { |
255 | { |
217 | for (;;) |
256 | for (;;) |
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226 | } |
265 | } |
227 | |
266 | |
228 | ... |
267 | ... |
229 | ev_set_allocator (persistent_realloc); |
268 | ev_set_allocator (persistent_realloc); |
230 | |
269 | |
231 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
232 | |
271 | |
233 | Set the callback function to call on a retryable syscall error (such |
272 | Set the callback function to call on a retryable system call error (such |
234 | as failed select, poll, epoll_wait). The message is a printable string |
273 | as failed select, poll, epoll_wait). The message is a printable string |
235 | indicating the system call or subsystem causing the problem. If this |
274 | indicating the system call or subsystem causing the problem. If this |
236 | callback is set, then libev will expect it to remedy the sitution, no |
275 | callback is set, then libev will expect it to remedy the situation, no |
237 | matter what, when it returns. That is, libev will generally retry the |
276 | matter what, when it returns. That is, libev will generally retry the |
238 | requested operation, or, if the condition doesn't go away, do bad stuff |
277 | requested operation, or, if the condition doesn't go away, do bad stuff |
239 | (such as abort). |
278 | (such as abort). |
240 | |
279 | |
241 | Example: This is basically the same thing that libev does internally, too. |
280 | Example: This is basically the same thing that libev does internally, too. |
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252 | |
291 | |
253 | =back |
292 | =back |
254 | |
293 | |
255 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
256 | |
295 | |
257 | An event loop is described by a C<struct ev_loop *>. The library knows two |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
258 | types of such loops, the I<default> loop, which supports signals and child |
297 | is I<not> optional in this case, as there is also an C<ev_loop> |
259 | events, and dynamically created loops which do not. |
298 | I<function>). |
260 | |
299 | |
261 | If you use threads, a common model is to run the default event loop |
300 | The library knows two types of such loops, the I<default> loop, which |
262 | in your main thread (or in a separate thread) and for each thread you |
301 | supports signals and child events, and dynamically created loops which do |
263 | create, you also create another event loop. Libev itself does no locking |
302 | not. |
264 | whatsoever, so if you mix calls to the same event loop in different |
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265 | threads, make sure you lock (this is usually a bad idea, though, even if |
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266 | done correctly, because it's hideous and inefficient). |
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267 | |
303 | |
268 | =over 4 |
304 | =over 4 |
269 | |
305 | |
270 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
271 | |
307 | |
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277 | If you don't know what event loop to use, use the one returned from this |
313 | If you don't know what event loop to use, use the one returned from this |
278 | function. |
314 | function. |
279 | |
315 | |
280 | Note that this function is I<not> thread-safe, so if you want to use it |
316 | Note that this function is I<not> thread-safe, so if you want to use it |
281 | from multiple threads, you have to lock (note also that this is unlikely, |
317 | from multiple threads, you have to lock (note also that this is unlikely, |
282 | as loops cannot bes hared easily between threads anyway). |
318 | as loops cannot be shared easily between threads anyway). |
283 | |
319 | |
284 | The default loop is the only loop that can handle C<ev_signal> and |
320 | The default loop is the only loop that can handle C<ev_signal> and |
285 | C<ev_child> watchers, and to do this, it always registers a handler |
321 | C<ev_child> watchers, and to do this, it always registers a handler |
286 | for C<SIGCHLD>. If this is a problem for your app you can either |
322 | for C<SIGCHLD>. If this is a problem for your application you can either |
287 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
288 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
324 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
289 | C<ev_default_init>. |
325 | C<ev_default_init>. |
290 | |
326 | |
291 | The flags argument can be used to specify special behaviour or specific |
327 | The flags argument can be used to specify special behaviour or specific |
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300 | The default flags value. Use this if you have no clue (it's the right |
336 | The default flags value. Use this if you have no clue (it's the right |
301 | thing, believe me). |
337 | thing, believe me). |
302 | |
338 | |
303 | =item C<EVFLAG_NOENV> |
339 | =item C<EVFLAG_NOENV> |
304 | |
340 | |
305 | If this flag bit is ored into the flag value (or the program runs setuid |
341 | If this flag bit is or'ed into the flag value (or the program runs setuid |
306 | or setgid) then libev will I<not> look at the environment variable |
342 | or setgid) then libev will I<not> look at the environment variable |
307 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
343 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
308 | override the flags completely if it is found in the environment. This is |
344 | override the flags completely if it is found in the environment. This is |
309 | useful to try out specific backends to test their performance, or to work |
345 | useful to try out specific backends to test their performance, or to work |
310 | around bugs. |
346 | around bugs. |
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317 | |
353 | |
318 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
319 | and thus this might slow down your event loop if you do a lot of loop |
355 | and thus this might slow down your event loop if you do a lot of loop |
320 | iterations and little real work, but is usually not noticeable (on my |
356 | iterations and little real work, but is usually not noticeable (on my |
321 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
322 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
358 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
323 | C<pthread_atfork> which is even faster). |
359 | C<pthread_atfork> which is even faster). |
324 | |
360 | |
325 | The big advantage of this flag is that you can forget about fork (and |
361 | The big advantage of this flag is that you can forget about fork (and |
326 | forget about forgetting to tell libev about forking) when you use this |
362 | forget about forgetting to tell libev about forking) when you use this |
327 | flag. |
363 | flag. |
328 | |
364 | |
329 | This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
330 | environment variable. |
366 | environment variable. |
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367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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|
375 | =item C<EVFLAG_SIGNALFD> |
|
|
376 | |
|
|
377 | 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 |
|
|
379 | 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 |
|
|
381 | handling with threads, as long as you properly block signals in your |
|
|
382 | threads that are not interested in handling them. |
|
|
383 | |
|
|
384 | 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 |
|
|
386 | example) that can't properly initialise their signal masks. |
331 | |
387 | |
332 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
333 | |
389 | |
334 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
335 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
336 | but if that fails, expect a fairly low limit on the number of fds when |
392 | but if that fails, expect a fairly low limit on the number of fds when |
337 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
393 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
338 | usually the fastest backend for a low number of (low-numbered :) fds. |
394 | usually the fastest backend for a low number of (low-numbered :) fds. |
339 | |
395 | |
340 | To get good performance out of this backend you need a high amount of |
396 | To get good performance out of this backend you need a high amount of |
341 | parallelity (most of the file descriptors should be busy). If you are |
397 | parallelism (most of the file descriptors should be busy). If you are |
342 | writing a server, you should C<accept ()> in a loop to accept as many |
398 | writing a server, you should C<accept ()> in a loop to accept as many |
343 | connections as possible during one iteration. You might also want to have |
399 | connections as possible during one iteration. You might also want to have |
344 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
400 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
345 | readyness notifications you get per iteration. |
401 | readiness notifications you get per iteration. |
|
|
402 | |
|
|
403 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
404 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
405 | C<exceptfds> set on that platform). |
346 | |
406 | |
347 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
407 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
348 | |
408 | |
349 | And this is your standard poll(2) backend. It's more complicated |
409 | And this is your standard poll(2) backend. It's more complicated |
350 | than select, but handles sparse fds better and has no artificial |
410 | than select, but handles sparse fds better and has no artificial |
351 | limit on the number of fds you can use (except it will slow down |
411 | limit on the number of fds you can use (except it will slow down |
352 | considerably with a lot of inactive fds). It scales similarly to select, |
412 | considerably with a lot of inactive fds). It scales similarly to select, |
353 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
413 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
354 | performance tips. |
414 | performance tips. |
355 | |
415 | |
|
|
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
418 | |
356 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
|
420 | |
|
|
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
422 | kernels). |
357 | |
423 | |
358 | For few fds, this backend is a bit little slower than poll and select, |
424 | For few fds, this backend is a bit little slower than poll and select, |
359 | but it scales phenomenally better. While poll and select usually scale |
425 | but it scales phenomenally better. While poll and select usually scale |
360 | like O(total_fds) where n is the total number of fds (or the highest fd), |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
361 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
427 | epoll scales either O(1) or O(active_fds). |
362 | of shortcomings, such as silently dropping events in some hard-to-detect |
428 | |
363 | cases and rewiring a syscall per fd change, no fork support and bad |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
364 | support for dup. |
430 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
431 | dropping file descriptors, requiring a system call per change per file |
|
|
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
433 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
434 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
435 | take considerable time (one syscall per file descriptor) and is of course |
|
|
436 | hard to detect. |
|
|
437 | |
|
|
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
439 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
440 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
441 | even remove them from the set) than registered in the set (especially |
|
|
442 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
443 | employing an additional generation counter and comparing that against the |
|
|
444 | events to filter out spurious ones, recreating the set when required. |
365 | |
445 | |
366 | While stopping, setting and starting an I/O watcher in the same iteration |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
367 | will result in some caching, there is still a syscall per such incident |
447 | will result in some caching, there is still a system call per such |
368 | (because the fd could point to a different file description now), so its |
448 | incident (because the same I<file descriptor> could point to a different |
369 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
370 | very well if you register events for both fds. |
450 | file descriptors might not work very well if you register events for both |
371 | |
451 | file descriptors. |
372 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
373 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
374 | (or space) is available. |
|
|
375 | |
452 | |
376 | Best performance from this backend is achieved by not unregistering all |
453 | Best performance from this backend is achieved by not unregistering all |
377 | watchers for a file descriptor until it has been closed, if possible, i.e. |
454 | watchers for a file descriptor until it has been closed, if possible, |
378 | keep at least one watcher active per fd at all times. |
455 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
456 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
457 | extra overhead. A fork can both result in spurious notifications as well |
|
|
458 | as in libev having to destroy and recreate the epoll object, which can |
|
|
459 | take considerable time and thus should be avoided. |
379 | |
460 | |
|
|
461 | 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 |
|
|
463 | the usage. So sad. |
|
|
464 | |
380 | While nominally embeddeble in other event loops, this feature is broken in |
465 | While nominally embeddable in other event loops, this feature is broken in |
381 | all kernel versions tested so far. |
466 | all kernel versions tested so far. |
|
|
467 | |
|
|
468 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
469 | C<EVBACKEND_POLL>. |
382 | |
470 | |
383 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
471 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
384 | |
472 | |
385 | Kqueue deserves special mention, as at the time of this writing, it |
473 | Kqueue deserves special mention, as at the time of this writing, it |
386 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
474 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
387 | with anything but sockets and pipes, except on Darwin, where of course |
475 | with anything but sockets and pipes, except on Darwin, where of course |
388 | it's completely useless). For this reason it's not being "autodetected" |
476 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
477 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
478 | without API changes to existing programs. For this reason it's not being |
389 | unless you explicitly specify it explicitly in the flags (i.e. using |
479 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
390 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
480 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
391 | system like NetBSD. |
481 | system like NetBSD. |
392 | |
482 | |
393 | You still can embed kqueue into a normal poll or select backend and use it |
483 | You still can embed kqueue into a normal poll or select backend and use it |
394 | only for sockets (after having made sure that sockets work with kqueue on |
484 | only for sockets (after having made sure that sockets work with kqueue on |
395 | the target platform). See C<ev_embed> watchers for more info. |
485 | the target platform). See C<ev_embed> watchers for more info. |
396 | |
486 | |
397 | It scales in the same way as the epoll backend, but the interface to the |
487 | It scales in the same way as the epoll backend, but the interface to the |
398 | kernel is more efficient (which says nothing about its actual speed, of |
488 | kernel is more efficient (which says nothing about its actual speed, of |
399 | course). While stopping, setting and starting an I/O watcher does never |
489 | course). While stopping, setting and starting an I/O watcher does never |
400 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
490 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
401 | two event changes per incident, support for C<fork ()> is very bad and it |
491 | two event changes per incident. Support for C<fork ()> is very bad (but |
402 | drops fds silently in similarly hard-to-detect cases. |
492 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
493 | cases |
403 | |
494 | |
404 | This backend usually performs well under most conditions. |
495 | This backend usually performs well under most conditions. |
405 | |
496 | |
406 | While nominally embeddable in other event loops, this doesn't work |
497 | While nominally embeddable in other event loops, this doesn't work |
407 | everywhere, so you might need to test for this. And since it is broken |
498 | everywhere, so you might need to test for this. And since it is broken |
408 | almost everywhere, you should only use it when you have a lot of sockets |
499 | almost everywhere, you should only use it when you have a lot of sockets |
409 | (for which it usually works), by embedding it into another event loop |
500 | (for which it usually works), by embedding it into another event loop |
410 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
501 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
411 | sockets. |
502 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
503 | |
|
|
504 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
505 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
506 | C<NOTE_EOF>. |
412 | |
507 | |
413 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
508 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
414 | |
509 | |
415 | This is not implemented yet (and might never be, unless you send me an |
510 | This is not implemented yet (and might never be, unless you send me an |
416 | implementation). According to reports, C</dev/poll> only supports sockets |
511 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
420 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
515 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
421 | |
516 | |
422 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
517 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
423 | it's really slow, but it still scales very well (O(active_fds)). |
518 | it's really slow, but it still scales very well (O(active_fds)). |
424 | |
519 | |
425 | Please note that solaris event ports can deliver a lot of spurious |
520 | Please note that Solaris event ports can deliver a lot of spurious |
426 | notifications, so you need to use non-blocking I/O or other means to avoid |
521 | notifications, so you need to use non-blocking I/O or other means to avoid |
427 | blocking when no data (or space) is available. |
522 | blocking when no data (or space) is available. |
428 | |
523 | |
429 | While this backend scales well, it requires one system call per active |
524 | While this backend scales well, it requires one system call per active |
430 | file descriptor per loop iteration. For small and medium numbers of file |
525 | file descriptor per loop iteration. For small and medium numbers of file |
431 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
526 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
432 | might perform better. |
527 | might perform better. |
433 | |
528 | |
434 | On the positive side, ignoring the spurious readyness notifications, this |
529 | On the positive side, with the exception of the spurious readiness |
435 | backend actually performed to specification in all tests and is fully |
530 | notifications, this backend actually performed fully to specification |
436 | embeddable, which is a rare feat among the OS-specific backends. |
531 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
532 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
533 | |
|
|
534 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
535 | C<EVBACKEND_POLL>. |
437 | |
536 | |
438 | =item C<EVBACKEND_ALL> |
537 | =item C<EVBACKEND_ALL> |
439 | |
538 | |
440 | Try all backends (even potentially broken ones that wouldn't be tried |
539 | Try all backends (even potentially broken ones that wouldn't be tried |
441 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
540 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
443 | |
542 | |
444 | It is definitely not recommended to use this flag. |
543 | It is definitely not recommended to use this flag. |
445 | |
544 | |
446 | =back |
545 | =back |
447 | |
546 | |
448 | If one or more of these are ored into the flags value, then only these |
547 | If one or more of the backend flags are or'ed into the flags value, |
449 | backends will be tried (in the reverse order as listed here). If none are |
548 | then only these backends will be tried (in the reverse order as listed |
450 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
550 | ()> will be tried. |
451 | |
551 | |
452 | The most typical usage is like this: |
552 | Example: This is the most typical usage. |
453 | |
553 | |
454 | if (!ev_default_loop (0)) |
554 | if (!ev_default_loop (0)) |
455 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
456 | |
556 | |
457 | Restrict libev to the select and poll backends, and do not allow |
557 | Example: Restrict libev to the select and poll backends, and do not allow |
458 | environment settings to be taken into account: |
558 | environment settings to be taken into account: |
459 | |
559 | |
460 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
560 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
461 | |
561 | |
462 | Use whatever libev has to offer, but make sure that kqueue is used if |
562 | Example: Use whatever libev has to offer, but make sure that kqueue is |
463 | available (warning, breaks stuff, best use only with your own private |
563 | used if available (warning, breaks stuff, best use only with your own |
464 | event loop and only if you know the OS supports your types of fds): |
564 | private event loop and only if you know the OS supports your types of |
|
|
565 | fds): |
465 | |
566 | |
466 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
467 | |
568 | |
468 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
469 | |
570 | |
470 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
471 | always distinct from the default loop. Unlike the default loop, it cannot |
572 | always distinct from the default loop. Unlike the default loop, it cannot |
… | |
… | |
476 | libev with threads is indeed to create one loop per thread, and using the |
577 | libev with threads is indeed to create one loop per thread, and using the |
477 | default loop in the "main" or "initial" thread. |
578 | default loop in the "main" or "initial" thread. |
478 | |
579 | |
479 | Example: Try to create a event loop that uses epoll and nothing else. |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
480 | |
581 | |
481 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
482 | if (!epoller) |
583 | if (!epoller) |
483 | fatal ("no epoll found here, maybe it hides under your chair"); |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
484 | |
585 | |
485 | =item ev_default_destroy () |
586 | =item ev_default_destroy () |
486 | |
587 | |
487 | Destroys the default loop again (frees all memory and kernel state |
588 | Destroys the default loop again (frees all memory and kernel state |
488 | etc.). None of the active event watchers will be stopped in the normal |
589 | etc.). None of the active event watchers will be stopped in the normal |
489 | sense, so e.g. C<ev_is_active> might still return true. It is your |
590 | sense, so e.g. C<ev_is_active> might still return true. It is your |
490 | responsibility to either stop all watchers cleanly yoursef I<before> |
591 | responsibility to either stop all watchers cleanly yourself I<before> |
491 | calling this function, or cope with the fact afterwards (which is usually |
592 | calling this function, or cope with the fact afterwards (which is usually |
492 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
593 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
493 | for example). |
594 | for example). |
494 | |
595 | |
495 | Note that certain global state, such as signal state, will not be freed by |
596 | Note that certain global state, such as signal state (and installed signal |
496 | this function, and related watchers (such as signal and child watchers) |
597 | handlers), will not be freed by this function, and related watchers (such |
497 | would need to be stopped manually. |
598 | as signal and child watchers) would need to be stopped manually. |
498 | |
599 | |
499 | In general it is not advisable to call this function except in the |
600 | In general it is not advisable to call this function except in the |
500 | rare occasion where you really need to free e.g. the signal handling |
601 | rare occasion where you really need to free e.g. the signal handling |
501 | pipe fds. If you need dynamically allocated loops it is better to use |
602 | pipe fds. If you need dynamically allocated loops it is better to use |
502 | C<ev_loop_new> and C<ev_loop_destroy>). |
603 | C<ev_loop_new> and C<ev_loop_destroy>. |
503 | |
604 | |
504 | =item ev_loop_destroy (loop) |
605 | =item ev_loop_destroy (loop) |
505 | |
606 | |
506 | Like C<ev_default_destroy>, but destroys an event loop created by an |
607 | Like C<ev_default_destroy>, but destroys an event loop created by an |
507 | earlier call to C<ev_loop_new>. |
608 | earlier call to C<ev_loop_new>. |
… | |
… | |
527 | |
628 | |
528 | =item ev_loop_fork (loop) |
629 | =item ev_loop_fork (loop) |
529 | |
630 | |
530 | Like C<ev_default_fork>, but acts on an event loop created by |
631 | Like C<ev_default_fork>, but acts on an event loop created by |
531 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
632 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
532 | after fork, and how you do this is entirely your own problem. |
633 | after fork that you want to re-use in the child, and how you do this is |
|
|
634 | entirely your own problem. |
533 | |
635 | |
534 | =item int ev_is_default_loop (loop) |
636 | =item int ev_is_default_loop (loop) |
535 | |
637 | |
536 | Returns true when the given loop actually is the default loop, false otherwise. |
638 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
639 | otherwise. |
537 | |
640 | |
538 | =item unsigned int ev_loop_count (loop) |
641 | =item unsigned int ev_loop_count (loop) |
539 | |
642 | |
540 | Returns the count of loop iterations for the loop, which is identical to |
643 | Returns the count of loop iterations for the loop, which is identical to |
541 | the number of times libev did poll for new events. It starts at C<0> and |
644 | the number of times libev did poll for new events. It starts at C<0> and |
542 | happily wraps around with enough iterations. |
645 | happily wraps around with enough iterations. |
543 | |
646 | |
544 | This value can sometimes be useful as a generation counter of sorts (it |
647 | This value can sometimes be useful as a generation counter of sorts (it |
545 | "ticks" the number of loop iterations), as it roughly corresponds with |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
546 | C<ev_prepare> and C<ev_check> calls. |
649 | C<ev_prepare> and C<ev_check> calls. |
|
|
650 | |
|
|
651 | =item unsigned int ev_loop_depth (loop) |
|
|
652 | |
|
|
653 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
654 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
655 | |
|
|
656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
658 | in which case it is higher. |
|
|
659 | |
|
|
660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
661 | etc.), doesn't count as exit. |
547 | |
662 | |
548 | =item unsigned int ev_backend (loop) |
663 | =item unsigned int ev_backend (loop) |
549 | |
664 | |
550 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
551 | use. |
666 | use. |
… | |
… | |
556 | received events and started processing them. This timestamp does not |
671 | received events and started processing them. This timestamp does not |
557 | change as long as callbacks are being processed, and this is also the base |
672 | change as long as callbacks are being processed, and this is also the base |
558 | time used for relative timers. You can treat it as the timestamp of the |
673 | time used for relative timers. You can treat it as the timestamp of the |
559 | event occurring (or more correctly, libev finding out about it). |
674 | event occurring (or more correctly, libev finding out about it). |
560 | |
675 | |
|
|
676 | =item ev_now_update (loop) |
|
|
677 | |
|
|
678 | 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 |
|
|
680 | is usually done automatically within C<ev_loop ()>. |
|
|
681 | |
|
|
682 | 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 |
|
|
684 | the current time is a good idea. |
|
|
685 | |
|
|
686 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
687 | |
|
|
688 | =item ev_suspend (loop) |
|
|
689 | |
|
|
690 | =item ev_resume (loop) |
|
|
691 | |
|
|
692 | These two functions suspend and resume a loop, for use when the loop is |
|
|
693 | not used for a while and timeouts should not be processed. |
|
|
694 | |
|
|
695 | 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 |
|
|
697 | 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> |
|
|
699 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
700 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
701 | |
|
|
702 | 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 |
|
|
704 | will be rescheduled (that is, they will lose any events that would have |
|
|
705 | occured while suspended). |
|
|
706 | |
|
|
707 | 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> |
|
|
709 | without a previous call to C<ev_suspend>. |
|
|
710 | |
|
|
711 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
712 | event loop time (see C<ev_now_update>). |
|
|
713 | |
561 | =item ev_loop (loop, int flags) |
714 | =item ev_loop (loop, int flags) |
562 | |
715 | |
563 | Finally, this is it, the event handler. This function usually is called |
716 | Finally, this is it, the event handler. This function usually is called |
564 | after you initialised all your watchers and you want to start handling |
717 | after you have initialised all your watchers and you want to start |
565 | events. |
718 | handling events. |
566 | |
719 | |
567 | If the flags argument is specified as C<0>, it will not return until |
720 | If the flags argument is specified as C<0>, it will not return until |
568 | either no event watchers are active anymore or C<ev_unloop> was called. |
721 | either no event watchers are active anymore or C<ev_unloop> was called. |
569 | |
722 | |
570 | Please note that an explicit C<ev_unloop> is usually better than |
723 | Please note that an explicit C<ev_unloop> is usually better than |
571 | relying on all watchers to be stopped when deciding when a program has |
724 | relying on all watchers to be stopped when deciding when a program has |
572 | finished (especially in interactive programs), but having a program that |
725 | finished (especially in interactive programs), but having a program |
573 | automatically loops as long as it has to and no longer by virtue of |
726 | that automatically loops as long as it has to and no longer by virtue |
574 | relying on its watchers stopping correctly is a thing of beauty. |
727 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
728 | beauty. |
575 | |
729 | |
576 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
730 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
577 | those events and any outstanding ones, but will not block your process in |
731 | those events and any already outstanding ones, but will not block your |
578 | case there are no events and will return after one iteration of the loop. |
732 | process in case there are no events and will return after one iteration of |
|
|
733 | the loop. |
579 | |
734 | |
580 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
735 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
581 | neccessary) and will handle those and any outstanding ones. It will block |
736 | necessary) and will handle those and any already outstanding ones. It |
582 | your process until at least one new event arrives, and will return after |
737 | will block your process until at least one new event arrives (which could |
583 | one iteration of the loop. This is useful if you are waiting for some |
738 | be an event internal to libev itself, so there is no guarantee that a |
584 | external event in conjunction with something not expressible using other |
739 | user-registered callback will be called), and will return after one |
|
|
740 | iteration of the loop. |
|
|
741 | |
|
|
742 | 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 |
585 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
744 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
586 | usually a better approach for this kind of thing. |
745 | usually a better approach for this kind of thing. |
587 | |
746 | |
588 | Here are the gory details of what C<ev_loop> does: |
747 | Here are the gory details of what C<ev_loop> does: |
589 | |
748 | |
590 | - Before the first iteration, call any pending watchers. |
749 | - Before the first iteration, call any pending watchers. |
591 | * If EVFLAG_FORKCHECK was used, check for a fork. |
750 | * If EVFLAG_FORKCHECK was used, check for a fork. |
592 | - If a fork was detected, queue and call all fork watchers. |
751 | - If a fork was detected (by any means), queue and call all fork watchers. |
593 | - Queue and call all prepare watchers. |
752 | - Queue and call all prepare watchers. |
594 | - If we have been forked, recreate the kernel state. |
753 | - If we have been forked, detach and recreate the kernel state |
|
|
754 | as to not disturb the other process. |
595 | - Update the kernel state with all outstanding changes. |
755 | - Update the kernel state with all outstanding changes. |
596 | - Update the "event loop time". |
756 | - Update the "event loop time" (ev_now ()). |
597 | - Calculate for how long to sleep or block, if at all |
757 | - Calculate for how long to sleep or block, if at all |
598 | (active idle watchers, EVLOOP_NONBLOCK or not having |
758 | (active idle watchers, EVLOOP_NONBLOCK or not having |
599 | any active watchers at all will result in not sleeping). |
759 | any active watchers at all will result in not sleeping). |
600 | - Sleep if the I/O and timer collect interval say so. |
760 | - Sleep if the I/O and timer collect interval say so. |
601 | - Block the process, waiting for any events. |
761 | - Block the process, waiting for any events. |
602 | - Queue all outstanding I/O (fd) events. |
762 | - Queue all outstanding I/O (fd) events. |
603 | - Update the "event loop time" and do time jump handling. |
763 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
604 | - Queue all outstanding timers. |
764 | - Queue all expired timers. |
605 | - Queue all outstanding periodics. |
765 | - Queue all expired periodics. |
606 | - If no events are pending now, queue all idle watchers. |
766 | - Unless any events are pending now, queue all idle watchers. |
607 | - Queue all check watchers. |
767 | - Queue all check watchers. |
608 | - Call all queued watchers in reverse order (i.e. check watchers first). |
768 | - Call all queued watchers in reverse order (i.e. check watchers first). |
609 | Signals and child watchers are implemented as I/O watchers, and will |
769 | Signals and child watchers are implemented as I/O watchers, and will |
610 | be handled here by queueing them when their watcher gets executed. |
770 | be handled here by queueing them when their watcher gets executed. |
611 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
771 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
… | |
… | |
616 | anymore. |
776 | anymore. |
617 | |
777 | |
618 | ... queue jobs here, make sure they register event watchers as long |
778 | ... queue jobs here, make sure they register event watchers as long |
619 | ... as they still have work to do (even an idle watcher will do..) |
779 | ... as they still have work to do (even an idle watcher will do..) |
620 | ev_loop (my_loop, 0); |
780 | ev_loop (my_loop, 0); |
621 | ... jobs done. yeah! |
781 | ... jobs done or somebody called unloop. yeah! |
622 | |
782 | |
623 | =item ev_unloop (loop, how) |
783 | =item ev_unloop (loop, how) |
624 | |
784 | |
625 | Can be used to make a call to C<ev_loop> return early (but only after it |
785 | Can be used to make a call to C<ev_loop> return early (but only after it |
626 | has processed all outstanding events). The C<how> argument must be either |
786 | has processed all outstanding events). The C<how> argument must be either |
627 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
787 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
628 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
788 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
629 | |
789 | |
630 | This "unloop state" will be cleared when entering C<ev_loop> again. |
790 | This "unloop state" will be cleared when entering C<ev_loop> again. |
631 | |
791 | |
|
|
792 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
793 | |
632 | =item ev_ref (loop) |
794 | =item ev_ref (loop) |
633 | |
795 | |
634 | =item ev_unref (loop) |
796 | =item ev_unref (loop) |
635 | |
797 | |
636 | Ref/unref can be used to add or remove a reference count on the event |
798 | Ref/unref can be used to add or remove a reference count on the event |
637 | loop: Every watcher keeps one reference, and as long as the reference |
799 | loop: Every watcher keeps one reference, and as long as the reference |
638 | count is nonzero, C<ev_loop> will not return on its own. If you have |
800 | count is nonzero, C<ev_loop> will not return on its own. |
639 | a watcher you never unregister that should not keep C<ev_loop> from |
801 | |
640 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
802 | 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 |
|
|
804 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
805 | before stopping it. |
|
|
806 | |
641 | example, libev itself uses this for its internal signal pipe: It is not |
807 | As an example, libev itself uses this for its internal signal pipe: It |
642 | visible to the libev user and should not keep C<ev_loop> from exiting if |
808 | is not visible to the libev user and should not keep C<ev_loop> from |
643 | no event watchers registered by it are active. It is also an excellent |
809 | exiting if no event watchers registered by it are active. It is also an |
644 | way to do this for generic recurring timers or from within third-party |
810 | excellent way to do this for generic recurring timers or from within |
645 | libraries. Just remember to I<unref after start> and I<ref before stop> |
811 | third-party libraries. Just remember to I<unref after start> and I<ref |
646 | (but only if the watcher wasn't active before, or was active before, |
812 | before stop> (but only if the watcher wasn't active before, or was active |
647 | respectively). |
813 | 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> |
|
|
815 | in the callback). |
648 | |
816 | |
649 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
817 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
650 | running when nothing else is active. |
818 | running when nothing else is active. |
651 | |
819 | |
652 | struct ev_signal exitsig; |
820 | ev_signal exitsig; |
653 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
821 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
654 | ev_signal_start (loop, &exitsig); |
822 | ev_signal_start (loop, &exitsig); |
655 | evf_unref (loop); |
823 | evf_unref (loop); |
656 | |
824 | |
657 | Example: For some weird reason, unregister the above signal handler again. |
825 | Example: For some weird reason, unregister the above signal handler again. |
658 | |
826 | |
659 | ev_ref (loop); |
827 | ev_ref (loop); |
660 | ev_signal_stop (loop, &exitsig); |
828 | ev_signal_stop (loop, &exitsig); |
661 | |
829 | |
662 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
830 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
663 | |
831 | |
664 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
832 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
665 | |
833 | |
666 | These advanced functions influence the time that libev will spend waiting |
834 | These advanced functions influence the time that libev will spend waiting |
667 | for events. Both are by default C<0>, meaning that libev will try to |
835 | for events. Both time intervals are by default C<0>, meaning that libev |
668 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
836 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
837 | latency. |
669 | |
838 | |
670 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
839 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
671 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
840 | allows libev to delay invocation of I/O and timer/periodic callbacks |
672 | increase efficiency of loop iterations. |
841 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
842 | opportunities). |
673 | |
843 | |
674 | The background is that sometimes your program runs just fast enough to |
844 | The idea is that sometimes your program runs just fast enough to handle |
675 | handle one (or very few) event(s) per loop iteration. While this makes |
845 | one (or very few) event(s) per loop iteration. While this makes the |
676 | the program responsive, it also wastes a lot of CPU time to poll for new |
846 | program responsive, it also wastes a lot of CPU time to poll for new |
677 | events, especially with backends like C<select ()> which have a high |
847 | events, especially with backends like C<select ()> which have a high |
678 | overhead for the actual polling but can deliver many events at once. |
848 | overhead for the actual polling but can deliver many events at once. |
679 | |
849 | |
680 | By setting a higher I<io collect interval> you allow libev to spend more |
850 | By setting a higher I<io collect interval> you allow libev to spend more |
681 | time collecting I/O events, so you can handle more events per iteration, |
851 | time collecting I/O events, so you can handle more events per iteration, |
682 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
852 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
683 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
853 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
684 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
854 | 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 |
|
|
856 | once per this interval, on average. |
685 | |
857 | |
686 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
858 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
687 | to spend more time collecting timeouts, at the expense of increased |
859 | to spend more time collecting timeouts, at the expense of increased |
688 | latency (the watcher callback will be called later). C<ev_io> watchers |
860 | latency/jitter/inexactness (the watcher callback will be called |
689 | will not be affected. Setting this to a non-null value will not introduce |
861 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
690 | any overhead in libev. |
862 | value will not introduce any overhead in libev. |
691 | |
863 | |
692 | Many (busy) programs can usually benefit by setting the io collect |
864 | Many (busy) programs can usually benefit by setting the I/O collect |
693 | interval to a value near C<0.1> or so, which is often enough for |
865 | interval to a value near C<0.1> or so, which is often enough for |
694 | interactive servers (of course not for games), likewise for timeouts. It |
866 | interactive servers (of course not for games), likewise for timeouts. It |
695 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
696 | as this approsaches the timing granularity of most systems. |
868 | 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 |
|
|
870 | 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, |
|
|
872 | then you can't do more than 100 transations per second). |
|
|
873 | |
|
|
874 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
875 | 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 |
|
|
877 | times the process sleeps and wakes up again. Another useful technique to |
|
|
878 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
879 | they fire on, say, one-second boundaries only. |
|
|
880 | |
|
|
881 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
882 | more often than 100 times per second: |
|
|
883 | |
|
|
884 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
885 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
886 | |
|
|
887 | =item ev_invoke_pending (loop) |
|
|
888 | |
|
|
889 | This call will simply invoke all pending watchers while resetting their |
|
|
890 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
891 | but when overriding the invoke callback this call comes handy. |
|
|
892 | |
|
|
893 | =item int ev_pending_count (loop) |
|
|
894 | |
|
|
895 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
896 | are pending. |
|
|
897 | |
|
|
898 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
899 | |
|
|
900 | 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 |
|
|
902 | this callback instead. This is useful, for example, when you want to |
|
|
903 | invoke the actual watchers inside another context (another thread etc.). |
|
|
904 | |
|
|
905 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
906 | callback. |
|
|
907 | |
|
|
908 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
909 | |
|
|
910 | 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 |
|
|
912 | each call to a libev function. |
|
|
913 | |
|
|
914 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
915 | wait for it to return. One way around this is to wake up the loop via |
|
|
916 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
917 | and I<acquire> callbacks on the loop. |
|
|
918 | |
|
|
919 | 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 |
|
|
921 | afterwards. |
|
|
922 | |
|
|
923 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
924 | C<acquire> will just call the mutex_lock function again. |
|
|
925 | |
|
|
926 | While event loop modifications are allowed between invocations of |
|
|
927 | 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 |
|
|
929 | 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 |
|
|
931 | to take note of any changes you made. |
|
|
932 | |
|
|
933 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
934 | invocations of C<release> and C<acquire>. |
|
|
935 | |
|
|
936 | See also the locking example in the C<THREADS> section later in this |
|
|
937 | document. |
|
|
938 | |
|
|
939 | =item ev_set_userdata (loop, void *data) |
|
|
940 | |
|
|
941 | =item ev_userdata (loop) |
|
|
942 | |
|
|
943 | 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 |
|
|
945 | C<0.> |
|
|
946 | |
|
|
947 | 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 |
|
|
949 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
950 | any other purpose as well. |
|
|
951 | |
|
|
952 | =item ev_loop_verify (loop) |
|
|
953 | |
|
|
954 | 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 |
|
|
956 | 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 |
|
|
958 | error and call C<abort ()>. |
|
|
959 | |
|
|
960 | This can be used to catch bugs inside libev itself: under normal |
|
|
961 | circumstances, this function will never abort as of course libev keeps its |
|
|
962 | data structures consistent. |
697 | |
963 | |
698 | =back |
964 | =back |
699 | |
965 | |
700 | |
966 | |
701 | =head1 ANATOMY OF A WATCHER |
967 | =head1 ANATOMY OF A WATCHER |
|
|
968 | |
|
|
969 | 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 |
|
|
971 | watchers and C<ev_io_start> for I/O watchers. |
702 | |
972 | |
703 | A watcher is a structure that you create and register to record your |
973 | A watcher is a structure that you create and register to record your |
704 | interest in some event. For instance, if you want to wait for STDIN to |
974 | interest in some event. For instance, if you want to wait for STDIN to |
705 | become readable, you would create an C<ev_io> watcher for that: |
975 | become readable, you would create an C<ev_io> watcher for that: |
706 | |
976 | |
707 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
977 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
708 | { |
978 | { |
709 | ev_io_stop (w); |
979 | ev_io_stop (w); |
710 | ev_unloop (loop, EVUNLOOP_ALL); |
980 | ev_unloop (loop, EVUNLOOP_ALL); |
711 | } |
981 | } |
712 | |
982 | |
713 | struct ev_loop *loop = ev_default_loop (0); |
983 | struct ev_loop *loop = ev_default_loop (0); |
|
|
984 | |
714 | struct ev_io stdin_watcher; |
985 | ev_io stdin_watcher; |
|
|
986 | |
715 | ev_init (&stdin_watcher, my_cb); |
987 | ev_init (&stdin_watcher, my_cb); |
716 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
988 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
717 | ev_io_start (loop, &stdin_watcher); |
989 | ev_io_start (loop, &stdin_watcher); |
|
|
990 | |
718 | ev_loop (loop, 0); |
991 | ev_loop (loop, 0); |
719 | |
992 | |
720 | As you can see, you are responsible for allocating the memory for your |
993 | As you can see, you are responsible for allocating the memory for your |
721 | watcher structures (and it is usually a bad idea to do this on the stack, |
994 | watcher structures (and it is I<usually> a bad idea to do this on the |
722 | although this can sometimes be quite valid). |
995 | stack). |
|
|
996 | |
|
|
997 | 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). |
723 | |
999 | |
724 | Each watcher structure must be initialised by a call to C<ev_init |
1000 | Each watcher structure must be initialised by a call to C<ev_init |
725 | (watcher *, callback)>, which expects a callback to be provided. This |
1001 | (watcher *, callback)>, which expects a callback to be provided. This |
726 | callback gets invoked each time the event occurs (or, in the case of io |
1002 | callback gets invoked each time the event occurs (or, in the case of I/O |
727 | watchers, each time the event loop detects that the file descriptor given |
1003 | watchers, each time the event loop detects that the file descriptor given |
728 | is readable and/or writable). |
1004 | is readable and/or writable). |
729 | |
1005 | |
730 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1006 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
731 | with arguments specific to this watcher type. There is also a macro |
1007 | macro to configure it, with arguments specific to the watcher type. There |
732 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1008 | is also a macro to combine initialisation and setting in one call: C<< |
733 | (watcher *, callback, ...) >>. |
1009 | ev_TYPE_init (watcher *, callback, ...) >>. |
734 | |
1010 | |
735 | To make the watcher actually watch out for events, you have to start it |
1011 | To make the watcher actually watch out for events, you have to start it |
736 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1012 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
737 | *) >>), and you can stop watching for events at any time by calling the |
1013 | *) >>), and you can stop watching for events at any time by calling the |
738 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1014 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
739 | |
1015 | |
740 | As long as your watcher is active (has been started but not stopped) you |
1016 | As long as your watcher is active (has been started but not stopped) you |
741 | must not touch the values stored in it. Most specifically you must never |
1017 | must not touch the values stored in it. Most specifically you must never |
742 | reinitialise it or call its C<set> macro. |
1018 | reinitialise it or call its C<ev_TYPE_set> macro. |
743 | |
1019 | |
744 | Each and every callback receives the event loop pointer as first, the |
1020 | Each and every callback receives the event loop pointer as first, the |
745 | registered watcher structure as second, and a bitset of received events as |
1021 | registered watcher structure as second, and a bitset of received events as |
746 | third argument. |
1022 | third argument. |
747 | |
1023 | |
… | |
… | |
805 | |
1081 | |
806 | =item C<EV_ASYNC> |
1082 | =item C<EV_ASYNC> |
807 | |
1083 | |
808 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1084 | The given async watcher has been asynchronously notified (see C<ev_async>). |
809 | |
1085 | |
|
|
1086 | =item C<EV_CUSTOM> |
|
|
1087 | |
|
|
1088 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1089 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1090 | |
810 | =item C<EV_ERROR> |
1091 | =item C<EV_ERROR> |
811 | |
1092 | |
812 | An unspecified error has occured, the watcher has been stopped. This might |
1093 | An unspecified error has occurred, the watcher has been stopped. This might |
813 | happen because the watcher could not be properly started because libev |
1094 | happen because the watcher could not be properly started because libev |
814 | ran out of memory, a file descriptor was found to be closed or any other |
1095 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1096 | problem. Libev considers these application bugs. |
|
|
1097 | |
815 | problem. You best act on it by reporting the problem and somehow coping |
1098 | You best act on it by reporting the problem and somehow coping with the |
816 | with the watcher being stopped. |
1099 | watcher being stopped. Note that well-written programs should not receive |
|
|
1100 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1101 | bug in your program. |
817 | |
1102 | |
818 | Libev will usually signal a few "dummy" events together with an error, |
1103 | Libev will usually signal a few "dummy" events together with an error, for |
819 | for example it might indicate that a fd is readable or writable, and if |
1104 | example it might indicate that a fd is readable or writable, and if your |
820 | your callbacks is well-written it can just attempt the operation and cope |
1105 | callbacks is well-written it can just attempt the operation and cope with |
821 | with the error from read() or write(). This will not work in multithreaded |
1106 | the error from read() or write(). This will not work in multi-threaded |
822 | programs, though, so beware. |
1107 | programs, though, as the fd could already be closed and reused for another |
|
|
1108 | thing, so beware. |
823 | |
1109 | |
824 | =back |
1110 | =back |
825 | |
1111 | |
826 | =head2 GENERIC WATCHER FUNCTIONS |
1112 | =head2 GENERIC WATCHER FUNCTIONS |
827 | |
|
|
828 | In the following description, C<TYPE> stands for the watcher type, |
|
|
829 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
830 | |
1113 | |
831 | =over 4 |
1114 | =over 4 |
832 | |
1115 | |
833 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1116 | =item C<ev_init> (ev_TYPE *watcher, callback) |
834 | |
1117 | |
… | |
… | |
840 | which rolls both calls into one. |
1123 | which rolls both calls into one. |
841 | |
1124 | |
842 | You can reinitialise a watcher at any time as long as it has been stopped |
1125 | You can reinitialise a watcher at any time as long as it has been stopped |
843 | (or never started) and there are no pending events outstanding. |
1126 | (or never started) and there are no pending events outstanding. |
844 | |
1127 | |
845 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1128 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
846 | int revents)>. |
1129 | int revents)>. |
847 | |
1130 | |
|
|
1131 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1132 | |
|
|
1133 | ev_io w; |
|
|
1134 | ev_init (&w, my_cb); |
|
|
1135 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1136 | |
848 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1137 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
849 | |
1138 | |
850 | This macro initialises the type-specific parts of a watcher. You need to |
1139 | This macro initialises the type-specific parts of a watcher. You need to |
851 | call C<ev_init> at least once before you call this macro, but you can |
1140 | call C<ev_init> at least once before you call this macro, but you can |
852 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1141 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
853 | macro on a watcher that is active (it can be pending, however, which is a |
1142 | macro on a watcher that is active (it can be pending, however, which is a |
854 | difference to the C<ev_init> macro). |
1143 | difference to the C<ev_init> macro). |
855 | |
1144 | |
856 | Although some watcher types do not have type-specific arguments |
1145 | Although some watcher types do not have type-specific arguments |
857 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1146 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
858 | |
1147 | |
|
|
1148 | See C<ev_init>, above, for an example. |
|
|
1149 | |
859 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1150 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
860 | |
1151 | |
861 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1152 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
862 | calls into a single call. This is the most convinient method to initialise |
1153 | calls into a single call. This is the most convenient method to initialise |
863 | a watcher. The same limitations apply, of course. |
1154 | a watcher. The same limitations apply, of course. |
864 | |
1155 | |
|
|
1156 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1157 | |
|
|
1158 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1159 | |
865 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1160 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
866 | |
1161 | |
867 | Starts (activates) the given watcher. Only active watchers will receive |
1162 | Starts (activates) the given watcher. Only active watchers will receive |
868 | events. If the watcher is already active nothing will happen. |
1163 | events. If the watcher is already active nothing will happen. |
869 | |
1164 | |
|
|
1165 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1166 | whole section. |
|
|
1167 | |
|
|
1168 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1169 | |
870 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1170 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
871 | |
1171 | |
872 | Stops the given watcher again (if active) and clears the pending |
1172 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1173 | the watcher was active or not). |
|
|
1174 | |
873 | status. It is possible that stopped watchers are pending (for example, |
1175 | It is possible that stopped watchers are pending - for example, |
874 | non-repeating timers are being stopped when they become pending), but |
1176 | non-repeating timers are being stopped when they become pending - but |
875 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1177 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
876 | you want to free or reuse the memory used by the watcher it is therefore a |
1178 | pending. If you want to free or reuse the memory used by the watcher it is |
877 | good idea to always call its C<ev_TYPE_stop> function. |
1179 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
878 | |
1180 | |
879 | =item bool ev_is_active (ev_TYPE *watcher) |
1181 | =item bool ev_is_active (ev_TYPE *watcher) |
880 | |
1182 | |
881 | Returns a true value iff the watcher is active (i.e. it has been started |
1183 | Returns a true value iff the watcher is active (i.e. it has been started |
882 | and not yet been stopped). As long as a watcher is active you must not modify |
1184 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
898 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1200 | =item ev_cb_set (ev_TYPE *watcher, callback) |
899 | |
1201 | |
900 | Change the callback. You can change the callback at virtually any time |
1202 | Change the callback. You can change the callback at virtually any time |
901 | (modulo threads). |
1203 | (modulo threads). |
902 | |
1204 | |
903 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1205 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
904 | |
1206 | |
905 | =item int ev_priority (ev_TYPE *watcher) |
1207 | =item int ev_priority (ev_TYPE *watcher) |
906 | |
1208 | |
907 | Set and query the priority of the watcher. The priority is a small |
1209 | Set and query the priority of the watcher. The priority is a small |
908 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1210 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
909 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1211 | (default: C<-2>). Pending watchers with higher priority will be invoked |
910 | before watchers with lower priority, but priority will not keep watchers |
1212 | before watchers with lower priority, but priority will not keep watchers |
911 | from being executed (except for C<ev_idle> watchers). |
1213 | from being executed (except for C<ev_idle> watchers). |
912 | |
1214 | |
913 | This means that priorities are I<only> used for ordering callback |
|
|
914 | invocation after new events have been received. This is useful, for |
|
|
915 | example, to reduce latency after idling, or more often, to bind two |
|
|
916 | watchers on the same event and make sure one is called first. |
|
|
917 | |
|
|
918 | If you need to suppress invocation when higher priority events are pending |
1215 | If you need to suppress invocation when higher priority events are pending |
919 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1216 | you need to look at C<ev_idle> watchers, which provide this functionality. |
920 | |
1217 | |
921 | You I<must not> change the priority of a watcher as long as it is active or |
1218 | You I<must not> change the priority of a watcher as long as it is active or |
922 | pending. |
1219 | pending. |
923 | |
1220 | |
|
|
1221 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1222 | fine, as long as you do not mind that the priority value you query might |
|
|
1223 | or might not have been clamped to the valid range. |
|
|
1224 | |
924 | The default priority used by watchers when no priority has been set is |
1225 | The default priority used by watchers when no priority has been set is |
925 | always C<0>, which is supposed to not be too high and not be too low :). |
1226 | always C<0>, which is supposed to not be too high and not be too low :). |
926 | |
1227 | |
927 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1228 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
928 | fine, as long as you do not mind that the priority value you query might |
1229 | priorities. |
929 | or might not have been adjusted to be within valid range. |
|
|
930 | |
1230 | |
931 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1231 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
932 | |
1232 | |
933 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1233 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
934 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1234 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
935 | can deal with that fact. |
1235 | can deal with that fact, as both are simply passed through to the |
|
|
1236 | callback. |
936 | |
1237 | |
937 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1238 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
938 | |
1239 | |
939 | If the watcher is pending, this function returns clears its pending status |
1240 | If the watcher is pending, this function clears its pending status and |
940 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1241 | returns its C<revents> bitset (as if its callback was invoked). If the |
941 | watcher isn't pending it does nothing and returns C<0>. |
1242 | watcher isn't pending it does nothing and returns C<0>. |
942 | |
1243 | |
|
|
1244 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1245 | callback to be invoked, which can be accomplished with this function. |
|
|
1246 | |
|
|
1247 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1248 | |
|
|
1249 | Feeds the given event set into the event loop, as if the specified event |
|
|
1250 | had happened for the specified watcher (which must be a pointer to an |
|
|
1251 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1252 | not free the watcher as long as it has pending events. |
|
|
1253 | |
|
|
1254 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1255 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1256 | not started in the first place. |
|
|
1257 | |
|
|
1258 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1259 | functions that do not need a watcher. |
|
|
1260 | |
943 | =back |
1261 | =back |
944 | |
1262 | |
945 | |
1263 | |
946 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1264 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
947 | |
1265 | |
948 | Each watcher has, by default, a member C<void *data> that you can change |
1266 | Each watcher has, by default, a member C<void *data> that you can change |
949 | and read at any time, libev will completely ignore it. This can be used |
1267 | and read at any time: libev will completely ignore it. This can be used |
950 | to associate arbitrary data with your watcher. If you need more data and |
1268 | to associate arbitrary data with your watcher. If you need more data and |
951 | don't want to allocate memory and store a pointer to it in that data |
1269 | don't want to allocate memory and store a pointer to it in that data |
952 | member, you can also "subclass" the watcher type and provide your own |
1270 | member, you can also "subclass" the watcher type and provide your own |
953 | data: |
1271 | data: |
954 | |
1272 | |
955 | struct my_io |
1273 | struct my_io |
956 | { |
1274 | { |
957 | struct ev_io io; |
1275 | ev_io io; |
958 | int otherfd; |
1276 | int otherfd; |
959 | void *somedata; |
1277 | void *somedata; |
960 | struct whatever *mostinteresting; |
1278 | struct whatever *mostinteresting; |
961 | } |
1279 | }; |
|
|
1280 | |
|
|
1281 | ... |
|
|
1282 | struct my_io w; |
|
|
1283 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
962 | |
1284 | |
963 | And since your callback will be called with a pointer to the watcher, you |
1285 | And since your callback will be called with a pointer to the watcher, you |
964 | can cast it back to your own type: |
1286 | can cast it back to your own type: |
965 | |
1287 | |
966 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1288 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
967 | { |
1289 | { |
968 | struct my_io *w = (struct my_io *)w_; |
1290 | struct my_io *w = (struct my_io *)w_; |
969 | ... |
1291 | ... |
970 | } |
1292 | } |
971 | |
1293 | |
972 | More interesting and less C-conformant ways of casting your callback type |
1294 | More interesting and less C-conformant ways of casting your callback type |
973 | instead have been omitted. |
1295 | instead have been omitted. |
974 | |
1296 | |
975 | Another common scenario is having some data structure with multiple |
1297 | Another common scenario is to use some data structure with multiple |
976 | watchers: |
1298 | embedded watchers: |
977 | |
1299 | |
978 | struct my_biggy |
1300 | struct my_biggy |
979 | { |
1301 | { |
980 | int some_data; |
1302 | int some_data; |
981 | ev_timer t1; |
1303 | ev_timer t1; |
982 | ev_timer t2; |
1304 | ev_timer t2; |
983 | } |
1305 | } |
984 | |
1306 | |
985 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1307 | In this case getting the pointer to C<my_biggy> is a bit more |
986 | you need to use C<offsetof>: |
1308 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1309 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1310 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1311 | programmers): |
987 | |
1312 | |
988 | #include <stddef.h> |
1313 | #include <stddef.h> |
989 | |
1314 | |
990 | static void |
1315 | static void |
991 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1316 | t1_cb (EV_P_ ev_timer *w, int revents) |
992 | { |
1317 | { |
993 | struct my_biggy big = (struct my_biggy * |
1318 | struct my_biggy big = (struct my_biggy *) |
994 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1319 | (((char *)w) - offsetof (struct my_biggy, t1)); |
995 | } |
1320 | } |
996 | |
1321 | |
997 | static void |
1322 | static void |
998 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1323 | t2_cb (EV_P_ ev_timer *w, int revents) |
999 | { |
1324 | { |
1000 | struct my_biggy big = (struct my_biggy * |
1325 | struct my_biggy big = (struct my_biggy *) |
1001 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1326 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1002 | } |
1327 | } |
|
|
1328 | |
|
|
1329 | =head2 WATCHER PRIORITY MODELS |
|
|
1330 | |
|
|
1331 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1332 | integers that influence the ordering of event callback invocation |
|
|
1333 | between watchers in some way, all else being equal. |
|
|
1334 | |
|
|
1335 | 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 |
|
|
1337 | range. |
|
|
1338 | |
|
|
1339 | There are two common ways how these these priorities are being interpreted |
|
|
1340 | by event loops: |
|
|
1341 | |
|
|
1342 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1343 | of lower priority watchers, which means as long as higher priority |
|
|
1344 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1345 | |
|
|
1346 | The less common only-for-ordering model uses priorities solely to order |
|
|
1347 | callback invocation within a single event loop iteration: Higher priority |
|
|
1348 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1349 | before polling for new events. |
|
|
1350 | |
|
|
1351 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1352 | except for idle watchers (which use the lock-out model). |
|
|
1353 | |
|
|
1354 | The rationale behind this is that implementing the lock-out model for |
|
|
1355 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1356 | libraries will just poll for the same events again and again as long as |
|
|
1357 | their callbacks have not been executed, which is very inefficient in the |
|
|
1358 | common case of one high-priority watcher locking out a mass of lower |
|
|
1359 | priority ones. |
|
|
1360 | |
|
|
1361 | Static (ordering) priorities are most useful when you have two or more |
|
|
1362 | watchers handling the same resource: a typical usage example is having an |
|
|
1363 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1364 | timeouts. Under load, data might be received while the program handles |
|
|
1365 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1366 | handler will be executed before checking for data. In that case, giving |
|
|
1367 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1368 | handled first even under adverse conditions (which is usually, but not |
|
|
1369 | always, what you want). |
|
|
1370 | |
|
|
1371 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1372 | will only be executed when no same or higher priority watchers have |
|
|
1373 | received events, they can be used to implement the "lock-out" model when |
|
|
1374 | required. |
|
|
1375 | |
|
|
1376 | 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 |
|
|
1378 | 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 |
|
|
1380 | continously 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 |
|
|
1382 | workable. |
|
|
1383 | |
|
|
1384 | 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, |
|
|
1386 | it might be preferable to stop the real watcher before starting the |
|
|
1387 | idle watcher, so the kernel will not have to process the event in case |
|
|
1388 | the actual processing will be delayed for considerable time. |
|
|
1389 | |
|
|
1390 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1391 | priority than the default, and which should only process data when no |
|
|
1392 | other events are pending: |
|
|
1393 | |
|
|
1394 | ev_idle idle; // actual processing watcher |
|
|
1395 | ev_io io; // actual event watcher |
|
|
1396 | |
|
|
1397 | static void |
|
|
1398 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1399 | { |
|
|
1400 | // stop the I/O watcher, we received the event, but |
|
|
1401 | // are not yet ready to handle it. |
|
|
1402 | ev_io_stop (EV_A_ w); |
|
|
1403 | |
|
|
1404 | // start the idle watcher to ahndle the actual event. |
|
|
1405 | // it will not be executed as long as other watchers |
|
|
1406 | // with the default priority are receiving events. |
|
|
1407 | ev_idle_start (EV_A_ &idle); |
|
|
1408 | } |
|
|
1409 | |
|
|
1410 | static void |
|
|
1411 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1412 | { |
|
|
1413 | // actual processing |
|
|
1414 | read (STDIN_FILENO, ...); |
|
|
1415 | |
|
|
1416 | // have to start the I/O watcher again, as |
|
|
1417 | // we have handled the event |
|
|
1418 | ev_io_start (EV_P_ &io); |
|
|
1419 | } |
|
|
1420 | |
|
|
1421 | // initialisation |
|
|
1422 | ev_idle_init (&idle, idle_cb); |
|
|
1423 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1424 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1425 | |
|
|
1426 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1427 | low-priority connections can not be locked out forever under load. This |
|
|
1428 | enables your program to keep a lower latency for important connections |
|
|
1429 | during short periods of high load, while not completely locking out less |
|
|
1430 | important ones. |
1003 | |
1431 | |
1004 | |
1432 | |
1005 | =head1 WATCHER TYPES |
1433 | =head1 WATCHER TYPES |
1006 | |
1434 | |
1007 | This section describes each watcher in detail, but will not repeat |
1435 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1031 | In general you can register as many read and/or write event watchers per |
1459 | In general you can register as many read and/or write event watchers per |
1032 | fd as you want (as long as you don't confuse yourself). Setting all file |
1460 | fd as you want (as long as you don't confuse yourself). Setting all file |
1033 | descriptors to non-blocking mode is also usually a good idea (but not |
1461 | descriptors to non-blocking mode is also usually a good idea (but not |
1034 | required if you know what you are doing). |
1462 | required if you know what you are doing). |
1035 | |
1463 | |
1036 | If you must do this, then force the use of a known-to-be-good backend |
1464 | If you cannot use non-blocking mode, then force the use of a |
1037 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1465 | known-to-be-good backend (at the time of this writing, this includes only |
1038 | C<EVBACKEND_POLL>). |
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. |
1039 | |
1469 | |
1040 | Another thing you have to watch out for is that it is quite easy to |
1470 | Another thing you have to watch out for is that it is quite easy to |
1041 | receive "spurious" readyness notifications, that is your callback might |
1471 | receive "spurious" readiness notifications, that is your callback might |
1042 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1043 | because there is no data. Not only are some backends known to create a |
1473 | because there is no data. Not only are some backends known to create a |
1044 | lot of those (for example solaris ports), it is very easy to get into |
1474 | lot of those (for example Solaris ports), it is very easy to get into |
1045 | this situation even with a relatively standard program structure. Thus |
1475 | this situation even with a relatively standard program structure. Thus |
1046 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1476 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1047 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1477 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1048 | |
1478 | |
1049 | If you cannot run the fd in non-blocking mode (for example you should not |
1479 | If you cannot run the fd in non-blocking mode (for example you should |
1050 | play around with an Xlib connection), then you have to seperately re-test |
1480 | not play around with an Xlib connection), then you have to separately |
1051 | whether a file descriptor is really ready with a known-to-be good interface |
1481 | re-test whether a file descriptor is really ready with a known-to-be good |
1052 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1482 | interface such as poll (fortunately in our Xlib example, Xlib already |
1053 | its own, so its quite safe to use). |
1483 | does 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 |
|
|
1485 | indefinitely. |
|
|
1486 | |
|
|
1487 | But really, best use non-blocking mode. |
1054 | |
1488 | |
1055 | =head3 The special problem of disappearing file descriptors |
1489 | =head3 The special problem of disappearing file descriptors |
1056 | |
1490 | |
1057 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1491 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1058 | descriptor (either by calling C<close> explicitly or by any other means, |
1492 | descriptor (either due to calling C<close> explicitly or any other means, |
1059 | such as C<dup>). The reason is that you register interest in some file |
1493 | such as C<dup2>). The reason is that you register interest in some file |
1060 | descriptor, but when it goes away, the operating system will silently drop |
1494 | descriptor, but when it goes away, the operating system will silently drop |
1061 | this interest. If another file descriptor with the same number then is |
1495 | this interest. If another file descriptor with the same number then is |
1062 | registered with libev, there is no efficient way to see that this is, in |
1496 | registered with libev, there is no efficient way to see that this is, in |
1063 | fact, a different file descriptor. |
1497 | fact, a different file descriptor. |
1064 | |
1498 | |
… | |
… | |
1095 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1529 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1096 | C<EVBACKEND_POLL>. |
1530 | C<EVBACKEND_POLL>. |
1097 | |
1531 | |
1098 | =head3 The special problem of SIGPIPE |
1532 | =head3 The special problem of SIGPIPE |
1099 | |
1533 | |
1100 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1534 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1101 | when reading from a pipe whose other end has been closed, your program |
1535 | when writing to a pipe whose other end has been closed, your program gets |
1102 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1536 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1103 | programs this is sensible behaviour, for daemons, this is usually |
1537 | this is sensible behaviour, for daemons, this is usually undesirable. |
1104 | undesirable. |
|
|
1105 | |
1538 | |
1106 | So when you encounter spurious, unexplained daemon exits, make sure you |
1539 | So when you encounter spurious, unexplained daemon exits, make sure you |
1107 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1540 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1108 | somewhere, as that would have given you a big clue). |
1541 | somewhere, as that would have given you a big clue). |
1109 | |
1542 | |
|
|
1543 | =head3 The special problem of accept()ing when you can't |
|
|
1544 | |
|
|
1545 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1546 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1547 | connection from the pending queue in all error cases. |
|
|
1548 | |
|
|
1549 | 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 |
|
|
1551 | rejecting the connection, leading to libev signalling readiness on |
|
|
1552 | the next iteration again (the connection still exists after all), and |
|
|
1553 | typically causing the program to loop at 100% CPU usage. |
|
|
1554 | |
|
|
1555 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1556 | operating systems, there is usually little the app can do to remedy the |
|
|
1557 | situation, and no known thread-safe method of removing the connection to |
|
|
1558 | cope with overload is known (to me). |
|
|
1559 | |
|
|
1560 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1561 | - when the program encounters an overload, it will just loop until the |
|
|
1562 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1563 | event-based way to handle this situation, so it's the best one can do. |
|
|
1564 | |
|
|
1565 | A better way to handle the situation is to log any errors other than |
|
|
1566 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1567 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1568 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1569 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1570 | usage. |
|
|
1571 | |
|
|
1572 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1573 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1574 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1575 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1576 | clients under typical overload conditions. |
|
|
1577 | |
|
|
1578 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1579 | is often done with C<malloc> failures, but this results in an easy |
|
|
1580 | opportunity for a DoS attack. |
1110 | |
1581 | |
1111 | =head3 Watcher-Specific Functions |
1582 | =head3 Watcher-Specific Functions |
1112 | |
1583 | |
1113 | =over 4 |
1584 | =over 4 |
1114 | |
1585 | |
1115 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1586 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1116 | |
1587 | |
1117 | =item ev_io_set (ev_io *, int fd, int events) |
1588 | =item ev_io_set (ev_io *, int fd, int events) |
1118 | |
1589 | |
1119 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1590 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1120 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1591 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1121 | C<EV_READ | EV_WRITE> to receive the given events. |
1592 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1122 | |
1593 | |
1123 | =item int fd [read-only] |
1594 | =item int fd [read-only] |
1124 | |
1595 | |
1125 | The file descriptor being watched. |
1596 | The file descriptor being watched. |
1126 | |
1597 | |
… | |
… | |
1134 | |
1605 | |
1135 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1606 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1136 | readable, but only once. Since it is likely line-buffered, you could |
1607 | readable, but only once. Since it is likely line-buffered, you could |
1137 | attempt to read a whole line in the callback. |
1608 | attempt to read a whole line in the callback. |
1138 | |
1609 | |
1139 | static void |
1610 | static void |
1140 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1611 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1141 | { |
1612 | { |
1142 | ev_io_stop (loop, w); |
1613 | ev_io_stop (loop, w); |
1143 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1614 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1144 | } |
1615 | } |
1145 | |
1616 | |
1146 | ... |
1617 | ... |
1147 | struct ev_loop *loop = ev_default_init (0); |
1618 | struct ev_loop *loop = ev_default_init (0); |
1148 | struct ev_io stdin_readable; |
1619 | ev_io stdin_readable; |
1149 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1620 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1150 | ev_io_start (loop, &stdin_readable); |
1621 | ev_io_start (loop, &stdin_readable); |
1151 | ev_loop (loop, 0); |
1622 | ev_loop (loop, 0); |
1152 | |
1623 | |
1153 | |
1624 | |
1154 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1625 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1155 | |
1626 | |
1156 | Timer watchers are simple relative timers that generate an event after a |
1627 | Timer watchers are simple relative timers that generate an event after a |
1157 | given time, and optionally repeating in regular intervals after that. |
1628 | given time, and optionally repeating in regular intervals after that. |
1158 | |
1629 | |
1159 | The timers are based on real time, that is, if you register an event that |
1630 | The timers are based on real time, that is, if you register an event that |
1160 | times out after an hour and you reset your system clock to last years |
1631 | times out after an hour and you reset your system clock to January last |
1161 | time, it will still time out after (roughly) and hour. "Roughly" because |
1632 | year, it will still time out after (roughly) one hour. "Roughly" because |
1162 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1633 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1163 | monotonic clock option helps a lot here). |
1634 | monotonic clock option helps a lot here). |
|
|
1635 | |
|
|
1636 | 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 |
|
|
1638 | might introduce a small delay). If multiple timers become ready during the |
|
|
1639 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1640 | before ones of the same priority with later time-out values (but this is |
|
|
1641 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1642 | |
|
|
1643 | =head3 Be smart about timeouts |
|
|
1644 | |
|
|
1645 | 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, |
|
|
1647 | you want to raise some error after a while. |
|
|
1648 | |
|
|
1649 | What follows are some ways to handle this problem, from obvious and |
|
|
1650 | inefficient to smart and efficient. |
|
|
1651 | |
|
|
1652 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1653 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1654 | data or other life sign was received). |
|
|
1655 | |
|
|
1656 | =over 4 |
|
|
1657 | |
|
|
1658 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1659 | |
|
|
1660 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1661 | start the watcher: |
|
|
1662 | |
|
|
1663 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1664 | ev_timer_start (loop, timer); |
|
|
1665 | |
|
|
1666 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1667 | and start it again: |
|
|
1668 | |
|
|
1669 | ev_timer_stop (loop, timer); |
|
|
1670 | ev_timer_set (timer, 60., 0.); |
|
|
1671 | ev_timer_start (loop, timer); |
|
|
1672 | |
|
|
1673 | This is relatively simple to implement, but means that each time there is |
|
|
1674 | some activity, libev will first have to remove the timer from its internal |
|
|
1675 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1676 | still not a constant-time operation. |
|
|
1677 | |
|
|
1678 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1679 | |
|
|
1680 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1681 | C<ev_timer_start>. |
|
|
1682 | |
|
|
1683 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1684 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1685 | successfully read or write some data. If you go into an idle state where |
|
|
1686 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1687 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1688 | |
|
|
1689 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1690 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1691 | member and C<ev_timer_again>. |
|
|
1692 | |
|
|
1693 | At start: |
|
|
1694 | |
|
|
1695 | ev_init (timer, callback); |
|
|
1696 | timer->repeat = 60.; |
|
|
1697 | ev_timer_again (loop, timer); |
|
|
1698 | |
|
|
1699 | Each time there is some activity: |
|
|
1700 | |
|
|
1701 | ev_timer_again (loop, timer); |
|
|
1702 | |
|
|
1703 | It is even possible to change the time-out on the fly, regardless of |
|
|
1704 | whether the watcher is active or not: |
|
|
1705 | |
|
|
1706 | timer->repeat = 30.; |
|
|
1707 | ev_timer_again (loop, timer); |
|
|
1708 | |
|
|
1709 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1710 | you want to modify its timeout value, as libev does not have to completely |
|
|
1711 | remove and re-insert the timer from/into its internal data structure. |
|
|
1712 | |
|
|
1713 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1714 | |
|
|
1715 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1716 | |
|
|
1717 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1718 | relatively long compared to the intervals between other activity - in |
|
|
1719 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1720 | associated activity resets. |
|
|
1721 | |
|
|
1722 | 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 |
|
|
1724 | within the callback: |
|
|
1725 | |
|
|
1726 | ev_tstamp last_activity; // time of last activity |
|
|
1727 | |
|
|
1728 | static void |
|
|
1729 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1730 | { |
|
|
1731 | ev_tstamp now = ev_now (EV_A); |
|
|
1732 | ev_tstamp timeout = last_activity + 60.; |
|
|
1733 | |
|
|
1734 | // if last_activity + 60. is older than now, we did time out |
|
|
1735 | if (timeout < now) |
|
|
1736 | { |
|
|
1737 | // timeout occured, take action |
|
|
1738 | } |
|
|
1739 | else |
|
|
1740 | { |
|
|
1741 | // callback was invoked, but there was some activity, re-arm |
|
|
1742 | // the watcher to fire in last_activity + 60, which is |
|
|
1743 | // guaranteed to be in the future, so "again" is positive: |
|
|
1744 | w->repeat = timeout - now; |
|
|
1745 | ev_timer_again (EV_A_ w); |
|
|
1746 | } |
|
|
1747 | } |
|
|
1748 | |
|
|
1749 | To summarise the callback: first calculate the real timeout (defined |
|
|
1750 | as "60 seconds after the last activity"), then check if that time has |
|
|
1751 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1752 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1753 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1754 | a timeout then. |
|
|
1755 | |
|
|
1756 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1757 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1758 | |
|
|
1759 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1760 | minus half the average time between activity), but virtually no calls to |
|
|
1761 | libev to change the timeout. |
|
|
1762 | |
|
|
1763 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1764 | to the current time (meaning we just have some activity :), then call the |
|
|
1765 | callback, which will "do the right thing" and start the timer: |
|
|
1766 | |
|
|
1767 | ev_init (timer, callback); |
|
|
1768 | last_activity = ev_now (loop); |
|
|
1769 | callback (loop, timer, EV_TIMEOUT); |
|
|
1770 | |
|
|
1771 | And when there is some activity, simply store the current time in |
|
|
1772 | C<last_activity>, no libev calls at all: |
|
|
1773 | |
|
|
1774 | last_actiivty = ev_now (loop); |
|
|
1775 | |
|
|
1776 | This technique is slightly more complex, but in most cases where the |
|
|
1777 | 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 | |
|
|
1783 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1784 | |
|
|
1785 | 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 |
|
|
1787 | do even better: |
|
|
1788 | |
|
|
1789 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1790 | at the I<end> of the list. |
|
|
1791 | |
|
|
1792 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1793 | the list is expected to fire (for example, using the technique #3). |
|
|
1794 | |
|
|
1795 | When there is some activity, remove the timer from the list, recalculate |
|
|
1796 | the timeout, append it to the end of the list again, and make sure to |
|
|
1797 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1798 | |
|
|
1799 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1800 | starting, stopping and updating the timers, at the expense of a major |
|
|
1801 | complication, and having to use a constant timeout. The constant timeout |
|
|
1802 | ensures that the list stays sorted. |
|
|
1803 | |
|
|
1804 | =back |
|
|
1805 | |
|
|
1806 | So which method the best? |
|
|
1807 | |
|
|
1808 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1809 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1810 | better, and isn't very complicated either. In most case, choosing either |
|
|
1811 | one is fine, with #3 being better in typical situations. |
|
|
1812 | |
|
|
1813 | 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 |
|
|
1815 | off after the first million or so of active timers, i.e. it's usually |
|
|
1816 | overkill :) |
|
|
1817 | |
|
|
1818 | =head3 The special problem of time updates |
|
|
1819 | |
|
|
1820 | Establishing the current time is a costly operation (it usually takes at |
|
|
1821 | least two system calls): EV therefore updates its idea of the current |
|
|
1822 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1823 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1824 | lots of events in one iteration. |
1164 | |
1825 | |
1165 | The relative timeouts are calculated relative to the C<ev_now ()> |
1826 | The relative timeouts are calculated relative to the C<ev_now ()> |
1166 | time. This is usually the right thing as this timestamp refers to the time |
1827 | time. This is usually the right thing as this timestamp refers to the time |
1167 | of the event triggering whatever timeout you are modifying/starting. If |
1828 | of the event triggering whatever timeout you are modifying/starting. If |
1168 | you suspect event processing to be delayed and you I<need> to base the timeout |
1829 | you suspect event processing to be delayed and you I<need> to base the |
1169 | on the current time, use something like this to adjust for this: |
1830 | timeout on the current time, use something like this to adjust for this: |
1170 | |
1831 | |
1171 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1832 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1172 | |
1833 | |
1173 | The callback is guarenteed to be invoked only when its timeout has passed, |
1834 | If the event loop is suspended for a long time, you can also force an |
1174 | but if multiple timers become ready during the same loop iteration then |
1835 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1175 | order of execution is undefined. |
1836 | ()>. |
|
|
1837 | |
|
|
1838 | =head3 The special problems of suspended animation |
|
|
1839 | |
|
|
1840 | 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? |
|
|
1842 | |
|
|
1843 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1844 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1845 | to run until the system is suspended, but they will not advance while the |
|
|
1846 | system is suspended. That means, on resume, it will be as if the program |
|
|
1847 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1848 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1849 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1850 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1851 | be adjusted accordingly. |
|
|
1852 | |
|
|
1853 | I would not be surprised to see different behaviour in different between |
|
|
1854 | operating systems, OS versions or even different hardware. |
|
|
1855 | |
|
|
1856 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1857 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1858 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1859 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1860 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1861 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1862 | |
|
|
1863 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1864 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1865 | deterministic behaviour in this case (you can do nothing against |
|
|
1866 | C<SIGSTOP>). |
1176 | |
1867 | |
1177 | =head3 Watcher-Specific Functions and Data Members |
1868 | =head3 Watcher-Specific Functions and Data Members |
1178 | |
1869 | |
1179 | =over 4 |
1870 | =over 4 |
1180 | |
1871 | |
1181 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1872 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1182 | |
1873 | |
1183 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1874 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1184 | |
1875 | |
1185 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1876 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1186 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1877 | is C<0.>, then it will automatically be stopped once the timeout is |
1187 | timer will automatically be configured to trigger again C<repeat> seconds |
1878 | reached. If it is positive, then the timer will automatically be |
1188 | later, again, and again, until stopped manually. |
1879 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1880 | until stopped manually. |
1189 | |
1881 | |
1190 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1882 | The timer itself will do a best-effort at avoiding drift, that is, if |
1191 | configure a timer to trigger every 10 seconds, then it will trigger at |
1883 | you configure a timer to trigger every 10 seconds, then it will normally |
1192 | exactly 10 second intervals. If, however, your program cannot keep up with |
1884 | trigger at exactly 10 second intervals. If, however, your program cannot |
1193 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1885 | keep up with the timer (because it takes longer than those 10 seconds to |
1194 | timer will not fire more than once per event loop iteration. |
1886 | do stuff) the timer will not fire more than once per event loop iteration. |
1195 | |
1887 | |
1196 | =item ev_timer_again (loop, ev_timer *) |
1888 | =item ev_timer_again (loop, ev_timer *) |
1197 | |
1889 | |
1198 | This will act as if the timer timed out and restart it again if it is |
1890 | This will act as if the timer timed out and restart it again if it is |
1199 | repeating. The exact semantics are: |
1891 | repeating. The exact semantics are: |
1200 | |
1892 | |
1201 | If the timer is pending, its pending status is cleared. |
1893 | If the timer is pending, its pending status is cleared. |
1202 | |
1894 | |
1203 | If the timer is started but nonrepeating, stop it (as if it timed out). |
1895 | If the timer is started but non-repeating, stop it (as if it timed out). |
1204 | |
1896 | |
1205 | If the timer is repeating, either start it if necessary (with the |
1897 | If the timer is repeating, either start it if necessary (with the |
1206 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1898 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1207 | |
1899 | |
1208 | This sounds a bit complicated, but here is a useful and typical |
1900 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1209 | example: Imagine you have a tcp connection and you want a so-called idle |
1901 | usage example. |
1210 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1211 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1212 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1213 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1214 | you go into an idle state where you do not expect data to travel on the |
|
|
1215 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1216 | automatically restart it if need be. |
|
|
1217 | |
1902 | |
1218 | That means you can ignore the C<after> value and C<ev_timer_start> |
1903 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1219 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1220 | |
1904 | |
1221 | ev_timer_init (timer, callback, 0., 5.); |
1905 | Returns the remaining time until a timer fires. If the timer is active, |
1222 | ev_timer_again (loop, timer); |
1906 | then this time is relative to the current event loop time, otherwise it's |
1223 | ... |
1907 | the timeout value currently configured. |
1224 | timer->again = 17.; |
|
|
1225 | ev_timer_again (loop, timer); |
|
|
1226 | ... |
|
|
1227 | timer->again = 10.; |
|
|
1228 | ev_timer_again (loop, timer); |
|
|
1229 | |
1908 | |
1230 | This is more slightly efficient then stopping/starting the timer each time |
1909 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1231 | you want to modify its timeout value. |
1910 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1911 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1912 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1913 | too), and so on. |
1232 | |
1914 | |
1233 | =item ev_tstamp repeat [read-write] |
1915 | =item ev_tstamp repeat [read-write] |
1234 | |
1916 | |
1235 | The current C<repeat> value. Will be used each time the watcher times out |
1917 | The current C<repeat> value. Will be used each time the watcher times out |
1236 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1918 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1237 | which is also when any modifications are taken into account. |
1919 | which is also when any modifications are taken into account. |
1238 | |
1920 | |
1239 | =back |
1921 | =back |
1240 | |
1922 | |
1241 | =head3 Examples |
1923 | =head3 Examples |
1242 | |
1924 | |
1243 | Example: Create a timer that fires after 60 seconds. |
1925 | Example: Create a timer that fires after 60 seconds. |
1244 | |
1926 | |
1245 | static void |
1927 | static void |
1246 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1928 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1247 | { |
1929 | { |
1248 | .. one minute over, w is actually stopped right here |
1930 | .. one minute over, w is actually stopped right here |
1249 | } |
1931 | } |
1250 | |
1932 | |
1251 | struct ev_timer mytimer; |
1933 | ev_timer mytimer; |
1252 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1934 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1253 | ev_timer_start (loop, &mytimer); |
1935 | ev_timer_start (loop, &mytimer); |
1254 | |
1936 | |
1255 | Example: Create a timeout timer that times out after 10 seconds of |
1937 | Example: Create a timeout timer that times out after 10 seconds of |
1256 | inactivity. |
1938 | inactivity. |
1257 | |
1939 | |
1258 | static void |
1940 | static void |
1259 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1941 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1260 | { |
1942 | { |
1261 | .. ten seconds without any activity |
1943 | .. ten seconds without any activity |
1262 | } |
1944 | } |
1263 | |
1945 | |
1264 | struct ev_timer mytimer; |
1946 | ev_timer mytimer; |
1265 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1947 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1266 | ev_timer_again (&mytimer); /* start timer */ |
1948 | ev_timer_again (&mytimer); /* start timer */ |
1267 | ev_loop (loop, 0); |
1949 | ev_loop (loop, 0); |
1268 | |
1950 | |
1269 | // and in some piece of code that gets executed on any "activity": |
1951 | // and in some piece of code that gets executed on any "activity": |
1270 | // reset the timeout to start ticking again at 10 seconds |
1952 | // reset the timeout to start ticking again at 10 seconds |
1271 | ev_timer_again (&mytimer); |
1953 | ev_timer_again (&mytimer); |
1272 | |
1954 | |
1273 | |
1955 | |
1274 | =head2 C<ev_periodic> - to cron or not to cron? |
1956 | =head2 C<ev_periodic> - to cron or not to cron? |
1275 | |
1957 | |
1276 | Periodic watchers are also timers of a kind, but they are very versatile |
1958 | Periodic watchers are also timers of a kind, but they are very versatile |
1277 | (and unfortunately a bit complex). |
1959 | (and unfortunately a bit complex). |
1278 | |
1960 | |
1279 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1961 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1280 | but on wallclock time (absolute time). You can tell a periodic watcher |
1962 | relative time, the physical time that passes) but on wall clock time |
1281 | to trigger "at" some specific point in time. For example, if you tell a |
1963 | (absolute time, the thing you can read on your calender or clock). The |
1282 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1964 | difference is that wall clock time can run faster or slower than real |
1283 | + 10.>) and then reset your system clock to the last year, then it will |
1965 | time, and time jumps are not uncommon (e.g. when you adjust your |
1284 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1966 | wrist-watch). |
1285 | roughly 10 seconds later). |
|
|
1286 | |
1967 | |
1287 | They can also be used to implement vastly more complex timers, such as |
1968 | You can tell a periodic watcher to trigger after some specific point |
1288 | triggering an event on each midnight, local time or other, complicated, |
1969 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
1289 | rules. |
1970 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1971 | not a delay) and then reset your system clock to January of the previous |
|
|
1972 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1973 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1974 | it, as it uses a relative timeout). |
1290 | |
1975 | |
|
|
1976 | 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 |
|
|
1978 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1979 | those cannot react to time jumps. |
|
|
1980 | |
1291 | As with timers, the callback is guarenteed to be invoked only when the |
1981 | As with timers, the callback is guaranteed to be invoked only when the |
1292 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1982 | point in time where it is supposed to trigger has passed. If multiple |
1293 | during the same loop iteration then order of execution is undefined. |
1983 | 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 |
|
|
1985 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1294 | |
1986 | |
1295 | =head3 Watcher-Specific Functions and Data Members |
1987 | =head3 Watcher-Specific Functions and Data Members |
1296 | |
1988 | |
1297 | =over 4 |
1989 | =over 4 |
1298 | |
1990 | |
1299 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1991 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1300 | |
1992 | |
1301 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1993 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1302 | |
1994 | |
1303 | Lots of arguments, lets sort it out... There are basically three modes of |
1995 | Lots of arguments, let's sort it out... There are basically three modes of |
1304 | operation, and we will explain them from simplest to complex: |
1996 | operation, and we will explain them from simplest to most complex: |
1305 | |
1997 | |
1306 | =over 4 |
1998 | =over 4 |
1307 | |
1999 | |
1308 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2000 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1309 | |
2001 | |
1310 | In this configuration the watcher triggers an event at the wallclock time |
2002 | In this configuration the watcher triggers an event after the wall clock |
1311 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
2003 | time C<offset> has passed. It will not repeat and will not adjust when a |
1312 | that is, if it is to be run at January 1st 2011 then it will run when the |
2004 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1313 | system time reaches or surpasses this time. |
2005 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2006 | this point in time. |
1314 | |
2007 | |
1315 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2008 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1316 | |
2009 | |
1317 | In this mode the watcher will always be scheduled to time out at the next |
2010 | In this mode the watcher will always be scheduled to time out at the next |
1318 | C<at + N * interval> time (for some integer N, which can also be negative) |
2011 | C<offset + N * interval> time (for some integer N, which can also be |
1319 | and then repeat, regardless of any time jumps. |
2012 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2013 | argument is merely an offset into the C<interval> periods. |
1320 | |
2014 | |
1321 | This can be used to create timers that do not drift with respect to system |
2015 | This can be used to create timers that do not drift with respect to the |
1322 | time: |
2016 | system clock, for example, here is an C<ev_periodic> that triggers each |
|
|
2017 | hour, on the hour (with respect to UTC): |
1323 | |
2018 | |
1324 | ev_periodic_set (&periodic, 0., 3600., 0); |
2019 | ev_periodic_set (&periodic, 0., 3600., 0); |
1325 | |
2020 | |
1326 | This doesn't mean there will always be 3600 seconds in between triggers, |
2021 | This doesn't mean there will always be 3600 seconds in between triggers, |
1327 | but only that the the callback will be called when the system time shows a |
2022 | but only that the callback will be called when the system time shows a |
1328 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2023 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1329 | by 3600. |
2024 | by 3600. |
1330 | |
2025 | |
1331 | Another way to think about it (for the mathematically inclined) is that |
2026 | Another way to think about it (for the mathematically inclined) is that |
1332 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2027 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1333 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2028 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1334 | |
2029 | |
1335 | For numerical stability it is preferable that the C<at> value is near |
2030 | For numerical stability it is preferable that the C<offset> value is near |
1336 | C<ev_now ()> (the current time), but there is no range requirement for |
2031 | C<ev_now ()> (the current time), but there is no range requirement for |
1337 | this value. |
2032 | this value, and in fact is often specified as zero. |
1338 | |
2033 | |
|
|
2034 | 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 |
|
|
2036 | 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). |
|
|
2038 | |
1339 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2039 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1340 | |
2040 | |
1341 | In this mode the values for C<interval> and C<at> are both being |
2041 | In this mode the values for C<interval> and C<offset> are both being |
1342 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2042 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1343 | reschedule callback will be called with the watcher as first, and the |
2043 | reschedule callback will be called with the watcher as first, and the |
1344 | current time as second argument. |
2044 | current time as second argument. |
1345 | |
2045 | |
1346 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2046 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1347 | ever, or make any event loop modifications>. If you need to stop it, |
2047 | or make ANY other event loop modifications whatsoever, unless explicitly |
1348 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
2048 | allowed by documentation here>. |
1349 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1350 | |
2049 | |
|
|
2050 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
2051 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
2052 | only event loop modification you are allowed to do). |
|
|
2053 | |
1351 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
2054 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1352 | ev_tstamp now)>, e.g.: |
2055 | *w, ev_tstamp now)>, e.g.: |
1353 | |
2056 | |
|
|
2057 | static ev_tstamp |
1354 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2058 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1355 | { |
2059 | { |
1356 | return now + 60.; |
2060 | return now + 60.; |
1357 | } |
2061 | } |
1358 | |
2062 | |
1359 | It must return the next time to trigger, based on the passed time value |
2063 | It must return the next time to trigger, based on the passed time value |
1360 | (that is, the lowest time value larger than to the second argument). It |
2064 | (that is, the lowest time value larger than to the second argument). It |
1361 | will usually be called just before the callback will be triggered, but |
2065 | will usually be called just before the callback will be triggered, but |
1362 | might be called at other times, too. |
2066 | might be called at other times, too. |
1363 | |
2067 | |
1364 | NOTE: I<< This callback must always return a time that is later than the |
2068 | NOTE: I<< This callback must always return a time that is higher than or |
1365 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
2069 | equal to the passed C<now> value >>. |
1366 | |
2070 | |
1367 | This can be used to create very complex timers, such as a timer that |
2071 | This can be used to create very complex timers, such as a timer that |
1368 | triggers on each midnight, local time. To do this, you would calculate the |
2072 | triggers on "next midnight, local time". To do this, you would calculate the |
1369 | next midnight after C<now> and return the timestamp value for this. How |
2073 | next midnight after C<now> and return the timestamp value for this. How |
1370 | you do this is, again, up to you (but it is not trivial, which is the main |
2074 | you do this is, again, up to you (but it is not trivial, which is the main |
1371 | reason I omitted it as an example). |
2075 | reason I omitted it as an example). |
1372 | |
2076 | |
1373 | =back |
2077 | =back |
… | |
… | |
1377 | Simply stops and restarts the periodic watcher again. This is only useful |
2081 | Simply stops and restarts the periodic watcher again. This is only useful |
1378 | when you changed some parameters or the reschedule callback would return |
2082 | when you changed some parameters or the reschedule callback would return |
1379 | a different time than the last time it was called (e.g. in a crond like |
2083 | a different time than the last time it was called (e.g. in a crond like |
1380 | program when the crontabs have changed). |
2084 | program when the crontabs have changed). |
1381 | |
2085 | |
|
|
2086 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
2087 | |
|
|
2088 | When active, returns the absolute time that the watcher is supposed |
|
|
2089 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2090 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2091 | rescheduling modes. |
|
|
2092 | |
1382 | =item ev_tstamp offset [read-write] |
2093 | =item ev_tstamp offset [read-write] |
1383 | |
2094 | |
1384 | When repeating, this contains the offset value, otherwise this is the |
2095 | When repeating, this contains the offset value, otherwise this is the |
1385 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2096 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2097 | although libev might modify this value for better numerical stability). |
1386 | |
2098 | |
1387 | Can be modified any time, but changes only take effect when the periodic |
2099 | Can be modified any time, but changes only take effect when the periodic |
1388 | timer fires or C<ev_periodic_again> is being called. |
2100 | timer fires or C<ev_periodic_again> is being called. |
1389 | |
2101 | |
1390 | =item ev_tstamp interval [read-write] |
2102 | =item ev_tstamp interval [read-write] |
1391 | |
2103 | |
1392 | The current interval value. Can be modified any time, but changes only |
2104 | The current interval value. Can be modified any time, but changes only |
1393 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2105 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1394 | called. |
2106 | called. |
1395 | |
2107 | |
1396 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2108 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1397 | |
2109 | |
1398 | The current reschedule callback, or C<0>, if this functionality is |
2110 | The current reschedule callback, or C<0>, if this functionality is |
1399 | switched off. Can be changed any time, but changes only take effect when |
2111 | switched off. Can be changed any time, but changes only take effect when |
1400 | the periodic timer fires or C<ev_periodic_again> is being called. |
2112 | the periodic timer fires or C<ev_periodic_again> is being called. |
1401 | |
2113 | |
1402 | =item ev_tstamp at [read-only] |
|
|
1403 | |
|
|
1404 | When active, contains the absolute time that the watcher is supposed to |
|
|
1405 | trigger next. |
|
|
1406 | |
|
|
1407 | =back |
2114 | =back |
1408 | |
2115 | |
1409 | =head3 Examples |
2116 | =head3 Examples |
1410 | |
2117 | |
1411 | Example: Call a callback every hour, or, more precisely, whenever the |
2118 | Example: Call a callback every hour, or, more precisely, whenever the |
1412 | system clock is divisible by 3600. The callback invocation times have |
2119 | system time is divisible by 3600. The callback invocation times have |
1413 | potentially a lot of jittering, but good long-term stability. |
2120 | potentially a lot of jitter, but good long-term stability. |
1414 | |
2121 | |
1415 | static void |
2122 | static void |
1416 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2123 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1417 | { |
2124 | { |
1418 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2125 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1419 | } |
2126 | } |
1420 | |
2127 | |
1421 | struct ev_periodic hourly_tick; |
2128 | ev_periodic hourly_tick; |
1422 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2129 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1423 | ev_periodic_start (loop, &hourly_tick); |
2130 | ev_periodic_start (loop, &hourly_tick); |
1424 | |
2131 | |
1425 | Example: The same as above, but use a reschedule callback to do it: |
2132 | Example: The same as above, but use a reschedule callback to do it: |
1426 | |
2133 | |
1427 | #include <math.h> |
2134 | #include <math.h> |
1428 | |
2135 | |
1429 | static ev_tstamp |
2136 | static ev_tstamp |
1430 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2137 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1431 | { |
2138 | { |
1432 | return fmod (now, 3600.) + 3600.; |
2139 | return now + (3600. - fmod (now, 3600.)); |
1433 | } |
2140 | } |
1434 | |
2141 | |
1435 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2142 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1436 | |
2143 | |
1437 | Example: Call a callback every hour, starting now: |
2144 | Example: Call a callback every hour, starting now: |
1438 | |
2145 | |
1439 | struct ev_periodic hourly_tick; |
2146 | ev_periodic hourly_tick; |
1440 | ev_periodic_init (&hourly_tick, clock_cb, |
2147 | ev_periodic_init (&hourly_tick, clock_cb, |
1441 | fmod (ev_now (loop), 3600.), 3600., 0); |
2148 | fmod (ev_now (loop), 3600.), 3600., 0); |
1442 | ev_periodic_start (loop, &hourly_tick); |
2149 | ev_periodic_start (loop, &hourly_tick); |
1443 | |
2150 | |
1444 | |
2151 | |
1445 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2152 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1446 | |
2153 | |
1447 | Signal watchers will trigger an event when the process receives a specific |
2154 | Signal watchers will trigger an event when the process receives a specific |
1448 | signal one or more times. Even though signals are very asynchronous, libev |
2155 | signal one or more times. Even though signals are very asynchronous, libev |
1449 | will try it's best to deliver signals synchronously, i.e. as part of the |
2156 | will try it's best to deliver signals synchronously, i.e. as part of the |
1450 | normal event processing, like any other event. |
2157 | normal event processing, like any other event. |
1451 | |
2158 | |
|
|
2159 | If you want signals to be delivered truly asynchronously, just use |
|
|
2160 | 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 |
|
|
2162 | synchronously wake up an event loop. |
|
|
2163 | |
1452 | You can configure as many watchers as you like per signal. Only when the |
2164 | You can configure as many watchers as you like for the same signal, but |
|
|
2165 | 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 |
|
|
2167 | 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. |
|
|
2169 | |
1453 | first watcher gets started will libev actually register a signal watcher |
2170 | When the first watcher gets started will libev actually register something |
1454 | with the kernel (thus it coexists with your own signal handlers as long |
2171 | with the kernel (thus it coexists with your own signal handlers as long as |
1455 | as you don't register any with libev). Similarly, when the last signal |
2172 | you don't register any with libev for the same signal). |
1456 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1457 | SIG_DFL (regardless of what it was set to before). |
|
|
1458 | |
2173 | |
1459 | If possible and supported, libev will install its handlers with |
2174 | If possible and supported, libev will install its handlers with |
1460 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
2175 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1461 | interrupted. If you have a problem with syscalls getting interrupted by |
2176 | not be unduly interrupted. If you have a problem with system calls getting |
1462 | signals you can block all signals in an C<ev_check> watcher and unblock |
2177 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1463 | them in an C<ev_prepare> watcher. |
2178 | and unblock them in an C<ev_prepare> watcher. |
|
|
2179 | |
|
|
2180 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2181 | |
|
|
2182 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2183 | (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, |
|
|
2185 | and might or might not set or restore the installed signal handler. |
|
|
2186 | |
|
|
2187 | 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 |
|
|
2189 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2190 | certain signals to be blocked. |
|
|
2191 | |
|
|
2192 | This means that before calling C<exec> (from the child) you should reset |
|
|
2193 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2194 | choice usually). |
|
|
2195 | |
|
|
2196 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2197 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2198 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2199 | |
|
|
2200 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2201 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2202 | the window of opportunity for problems, it will not go away, as libev |
|
|
2203 | I<has> to modify the signal mask, at least temporarily. |
|
|
2204 | |
|
|
2205 | 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 |
|
|
2207 | is not a libev-specific thing, this is true for most event libraries. |
1464 | |
2208 | |
1465 | =head3 Watcher-Specific Functions and Data Members |
2209 | =head3 Watcher-Specific Functions and Data Members |
1466 | |
2210 | |
1467 | =over 4 |
2211 | =over 4 |
1468 | |
2212 | |
… | |
… | |
1479 | |
2223 | |
1480 | =back |
2224 | =back |
1481 | |
2225 | |
1482 | =head3 Examples |
2226 | =head3 Examples |
1483 | |
2227 | |
1484 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2228 | Example: Try to exit cleanly on SIGINT. |
1485 | |
2229 | |
1486 | static void |
2230 | static void |
1487 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2231 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1488 | { |
2232 | { |
1489 | ev_unloop (loop, EVUNLOOP_ALL); |
2233 | ev_unloop (loop, EVUNLOOP_ALL); |
1490 | } |
2234 | } |
1491 | |
2235 | |
1492 | struct ev_signal signal_watcher; |
2236 | ev_signal signal_watcher; |
1493 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2237 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1494 | ev_signal_start (loop, &sigint_cb); |
2238 | ev_signal_start (loop, &signal_watcher); |
1495 | |
2239 | |
1496 | |
2240 | |
1497 | =head2 C<ev_child> - watch out for process status changes |
2241 | =head2 C<ev_child> - watch out for process status changes |
1498 | |
2242 | |
1499 | Child watchers trigger when your process receives a SIGCHLD in response to |
2243 | Child watchers trigger when your process receives a SIGCHLD in response to |
1500 | some child status changes (most typically when a child of yours dies). It |
2244 | some child status changes (most typically when a child of yours dies or |
1501 | is permissible to install a child watcher I<after> the child has been |
2245 | exits). It is permissible to install a child watcher I<after> the child |
1502 | forked (which implies it might have already exited), as long as the event |
2246 | has been forked (which implies it might have already exited), as long |
1503 | loop isn't entered (or is continued from a watcher). |
2247 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2248 | forking and then immediately registering a watcher for the child is fine, |
|
|
2249 | but forking and registering a watcher a few event loop iterations later or |
|
|
2250 | in the next callback invocation is not. |
1504 | |
2251 | |
1505 | Only the default event loop is capable of handling signals, and therefore |
2252 | Only the default event loop is capable of handling signals, and therefore |
1506 | you can only rgeister child watchers in the default event loop. |
2253 | you can only register child watchers in the default event loop. |
|
|
2254 | |
|
|
2255 | Due to some design glitches inside libev, child watchers will always be |
|
|
2256 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2257 | libev) |
1507 | |
2258 | |
1508 | =head3 Process Interaction |
2259 | =head3 Process Interaction |
1509 | |
2260 | |
1510 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2261 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1511 | initialised. This is necessary to guarantee proper behaviour even if |
2262 | initialised. This is necessary to guarantee proper behaviour even if the |
1512 | the first child watcher is started after the child exits. The occurance |
2263 | first child watcher is started after the child exits. The occurrence |
1513 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2264 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1514 | synchronously as part of the event loop processing. Libev always reaps all |
2265 | synchronously as part of the event loop processing. Libev always reaps all |
1515 | children, even ones not watched. |
2266 | children, even ones not watched. |
1516 | |
2267 | |
1517 | =head3 Overriding the Built-In Processing |
2268 | =head3 Overriding the Built-In Processing |
… | |
… | |
1521 | handler, you can override it easily by installing your own handler for |
2272 | handler, you can override it easily by installing your own handler for |
1522 | C<SIGCHLD> after initialising the default loop, and making sure the |
2273 | C<SIGCHLD> after initialising the default loop, and making sure the |
1523 | default loop never gets destroyed. You are encouraged, however, to use an |
2274 | default loop never gets destroyed. You are encouraged, however, to use an |
1524 | event-based approach to child reaping and thus use libev's support for |
2275 | event-based approach to child reaping and thus use libev's support for |
1525 | that, so other libev users can use C<ev_child> watchers freely. |
2276 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2277 | |
|
|
2278 | =head3 Stopping the Child Watcher |
|
|
2279 | |
|
|
2280 | Currently, the child watcher never gets stopped, even when the |
|
|
2281 | child terminates, so normally one needs to stop the watcher in the |
|
|
2282 | callback. Future versions of libev might stop the watcher automatically |
|
|
2283 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2284 | problem). |
1526 | |
2285 | |
1527 | =head3 Watcher-Specific Functions and Data Members |
2286 | =head3 Watcher-Specific Functions and Data Members |
1528 | |
2287 | |
1529 | =over 4 |
2288 | =over 4 |
1530 | |
2289 | |
… | |
… | |
1559 | =head3 Examples |
2318 | =head3 Examples |
1560 | |
2319 | |
1561 | Example: C<fork()> a new process and install a child handler to wait for |
2320 | Example: C<fork()> a new process and install a child handler to wait for |
1562 | its completion. |
2321 | its completion. |
1563 | |
2322 | |
1564 | ev_child cw; |
2323 | ev_child cw; |
1565 | |
2324 | |
1566 | static void |
2325 | static void |
1567 | child_cb (EV_P_ struct ev_child *w, int revents) |
2326 | child_cb (EV_P_ ev_child *w, int revents) |
1568 | { |
2327 | { |
1569 | ev_child_stop (EV_A_ w); |
2328 | ev_child_stop (EV_A_ w); |
1570 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2329 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1571 | } |
2330 | } |
1572 | |
2331 | |
1573 | pid_t pid = fork (); |
2332 | pid_t pid = fork (); |
1574 | |
2333 | |
1575 | if (pid < 0) |
2334 | if (pid < 0) |
1576 | // error |
2335 | // error |
1577 | else if (pid == 0) |
2336 | else if (pid == 0) |
1578 | { |
2337 | { |
1579 | // the forked child executes here |
2338 | // the forked child executes here |
1580 | exit (1); |
2339 | exit (1); |
1581 | } |
2340 | } |
1582 | else |
2341 | else |
1583 | { |
2342 | { |
1584 | ev_child_init (&cw, child_cb, pid, 0); |
2343 | ev_child_init (&cw, child_cb, pid, 0); |
1585 | ev_child_start (EV_DEFAULT_ &cw); |
2344 | ev_child_start (EV_DEFAULT_ &cw); |
1586 | } |
2345 | } |
1587 | |
2346 | |
1588 | |
2347 | |
1589 | =head2 C<ev_stat> - did the file attributes just change? |
2348 | =head2 C<ev_stat> - did the file attributes just change? |
1590 | |
2349 | |
1591 | This watches a filesystem path for attribute changes. That is, it calls |
2350 | This watches a file system path for attribute changes. That is, it calls |
1592 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2351 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1593 | compared to the last time, invoking the callback if it did. |
2352 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2353 | it did. |
1594 | |
2354 | |
1595 | The path does not need to exist: changing from "path exists" to "path does |
2355 | The path does not need to exist: changing from "path exists" to "path does |
1596 | not exist" is a status change like any other. The condition "path does |
2356 | not exist" is a status change like any other. The condition "path does not |
1597 | not exist" is signified by the C<st_nlink> field being zero (which is |
2357 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1598 | otherwise always forced to be at least one) and all the other fields of |
2358 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1599 | the stat buffer having unspecified contents. |
2359 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2360 | contents. |
1600 | |
2361 | |
1601 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2362 | The path I<must not> end in a slash or contain special components such as |
|
|
2363 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1602 | relative and your working directory changes, the behaviour is undefined. |
2364 | your working directory changes, then the behaviour is undefined. |
1603 | |
2365 | |
1604 | Since there is no standard to do this, the portable implementation simply |
2366 | Since there is no portable change notification interface available, the |
1605 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2367 | portable implementation simply calls C<stat(2)> regularly on the path |
1606 | can specify a recommended polling interval for this case. If you specify |
2368 | to see if it changed somehow. You can specify a recommended polling |
1607 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2369 | interval for this case. If you specify a polling interval of C<0> (highly |
1608 | unspecified default> value will be used (which you can expect to be around |
2370 | recommended!) then a I<suitable, unspecified default> value will be used |
1609 | five seconds, although this might change dynamically). Libev will also |
2371 | (which you can expect to be around five seconds, although this might |
1610 | impose a minimum interval which is currently around C<0.1>, but thats |
2372 | change dynamically). Libev will also impose a minimum interval which is |
1611 | usually overkill. |
2373 | currently around C<0.1>, but that's usually overkill. |
1612 | |
2374 | |
1613 | This watcher type is not meant for massive numbers of stat watchers, |
2375 | This watcher type is not meant for massive numbers of stat watchers, |
1614 | as even with OS-supported change notifications, this can be |
2376 | as even with OS-supported change notifications, this can be |
1615 | resource-intensive. |
2377 | resource-intensive. |
1616 | |
2378 | |
1617 | At the time of this writing, only the Linux inotify interface is |
2379 | At the time of this writing, the only OS-specific interface implemented |
1618 | implemented (implementing kqueue support is left as an exercise for the |
2380 | is the Linux inotify interface (implementing kqueue support is left as an |
1619 | reader). Inotify will be used to give hints only and should not change the |
2381 | exercise for the reader. Note, however, that the author sees no way of |
1620 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
2382 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1621 | to fall back to regular polling again even with inotify, but changes are |
|
|
1622 | usually detected immediately, and if the file exists there will be no |
|
|
1623 | polling. |
|
|
1624 | |
2383 | |
1625 | =head3 ABI Issues (Largefile Support) |
2384 | =head3 ABI Issues (Largefile Support) |
1626 | |
2385 | |
1627 | Libev by default (unless the user overrides this) uses the default |
2386 | Libev by default (unless the user overrides this) uses the default |
1628 | compilation environment, which means that on systems with optionally |
2387 | compilation environment, which means that on systems with large file |
1629 | disabled large file support, you get the 32 bit version of the stat |
2388 | support disabled by default, you get the 32 bit version of the stat |
1630 | structure. When using the library from programs that change the ABI to |
2389 | structure. When using the library from programs that change the ABI to |
1631 | use 64 bit file offsets the programs will fail. In that case you have to |
2390 | use 64 bit file offsets the programs will fail. In that case you have to |
1632 | compile libev with the same flags to get binary compatibility. This is |
2391 | compile libev with the same flags to get binary compatibility. This is |
1633 | obviously the case with any flags that change the ABI, but the problem is |
2392 | obviously the case with any flags that change the ABI, but the problem is |
1634 | most noticably with ev_stat and largefile support. |
2393 | most noticeably displayed with ev_stat and large file support. |
1635 | |
2394 | |
1636 | =head3 Inotify |
2395 | The solution for this is to lobby your distribution maker to make large |
|
|
2396 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2397 | optional. Libev cannot simply switch on large file support because it has |
|
|
2398 | to exchange stat structures with application programs compiled using the |
|
|
2399 | default compilation environment. |
1637 | |
2400 | |
|
|
2401 | =head3 Inotify and Kqueue |
|
|
2402 | |
1638 | When C<inotify (7)> support has been compiled into libev (generally only |
2403 | When C<inotify (7)> support has been compiled into libev and present at |
1639 | available on Linux) and present at runtime, it will be used to speed up |
2404 | runtime, it will be used to speed up change detection where possible. The |
1640 | change detection where possible. The inotify descriptor will be created lazily |
2405 | inotify descriptor will be created lazily when the first C<ev_stat> |
1641 | when the first C<ev_stat> watcher is being started. |
2406 | watcher is being started. |
1642 | |
2407 | |
1643 | Inotify presense does not change the semantics of C<ev_stat> watchers |
2408 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1644 | except that changes might be detected earlier, and in some cases, to avoid |
2409 | except that changes might be detected earlier, and in some cases, to avoid |
1645 | making regular C<stat> calls. Even in the presense of inotify support |
2410 | making regular C<stat> calls. Even in the presence of inotify support |
1646 | there are many cases where libev has to resort to regular C<stat> polling. |
2411 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2412 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2413 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2414 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2415 | xfs are fully working) libev usually gets away without polling. |
1647 | |
2416 | |
1648 | (There is no support for kqueue, as apparently it cannot be used to |
2417 | There is no support for kqueue, as apparently it cannot be used to |
1649 | implement this functionality, due to the requirement of having a file |
2418 | implement this functionality, due to the requirement of having a file |
1650 | descriptor open on the object at all times). |
2419 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2420 | etc. is difficult. |
|
|
2421 | |
|
|
2422 | =head3 C<stat ()> is a synchronous operation |
|
|
2423 | |
|
|
2424 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2425 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2426 | ()>, which is a synchronous operation. |
|
|
2427 | |
|
|
2428 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2429 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2430 | as the path data is usually in memory already (except when starting the |
|
|
2431 | watcher). |
|
|
2432 | |
|
|
2433 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2434 | time due to network issues, and even under good conditions, a stat call |
|
|
2435 | often takes multiple milliseconds. |
|
|
2436 | |
|
|
2437 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2438 | paths, although this is fully supported by libev. |
1651 | |
2439 | |
1652 | =head3 The special problem of stat time resolution |
2440 | =head3 The special problem of stat time resolution |
1653 | |
2441 | |
1654 | The C<stat ()> syscall only supports full-second resolution portably, and |
2442 | The C<stat ()> system call only supports full-second resolution portably, |
1655 | even on systems where the resolution is higher, many filesystems still |
2443 | and even on systems where the resolution is higher, most file systems |
1656 | only support whole seconds. |
2444 | still only support whole seconds. |
1657 | |
2445 | |
1658 | That means that, if the time is the only thing that changes, you might |
2446 | That means that, if the time is the only thing that changes, you can |
1659 | miss updates: on the first update, C<ev_stat> detects a change and calls |
2447 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1660 | your callback, which does something. When there is another update within |
2448 | calls your callback, which does something. When there is another update |
1661 | the same second, C<ev_stat> will be unable to detect it. |
2449 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2450 | stat data does change in other ways (e.g. file size). |
1662 | |
2451 | |
1663 | The solution to this is to delay acting on a change for a second (or till |
2452 | The solution to this is to delay acting on a change for slightly more |
1664 | the next second boundary), using a roughly one-second delay C<ev_timer> |
2453 | than a second (or till slightly after the next full second boundary), using |
1665 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
2454 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1666 | is added to work around small timing inconsistencies of some operating |
2455 | ev_timer_again (loop, w)>). |
1667 | systems. |
2456 | |
|
|
2457 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2458 | of some operating systems (where the second counter of the current time |
|
|
2459 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2460 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2461 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2462 | update file times then there will be a small window where the kernel uses |
|
|
2463 | the previous second to update file times but libev might already execute |
|
|
2464 | the timer callback). |
1668 | |
2465 | |
1669 | =head3 Watcher-Specific Functions and Data Members |
2466 | =head3 Watcher-Specific Functions and Data Members |
1670 | |
2467 | |
1671 | =over 4 |
2468 | =over 4 |
1672 | |
2469 | |
… | |
… | |
1678 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2475 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1679 | be detected and should normally be specified as C<0> to let libev choose |
2476 | be detected and should normally be specified as C<0> to let libev choose |
1680 | a suitable value. The memory pointed to by C<path> must point to the same |
2477 | a suitable value. The memory pointed to by C<path> must point to the same |
1681 | path for as long as the watcher is active. |
2478 | path for as long as the watcher is active. |
1682 | |
2479 | |
1683 | The callback will be receive C<EV_STAT> when a change was detected, |
2480 | The callback will receive an C<EV_STAT> event when a change was detected, |
1684 | relative to the attributes at the time the watcher was started (or the |
2481 | relative to the attributes at the time the watcher was started (or the |
1685 | last change was detected). |
2482 | last change was detected). |
1686 | |
2483 | |
1687 | =item ev_stat_stat (loop, ev_stat *) |
2484 | =item ev_stat_stat (loop, ev_stat *) |
1688 | |
2485 | |
1689 | Updates the stat buffer immediately with new values. If you change the |
2486 | Updates the stat buffer immediately with new values. If you change the |
1690 | watched path in your callback, you could call this fucntion to avoid |
2487 | watched path in your callback, you could call this function to avoid |
1691 | detecting this change (while introducing a race condition). Can also be |
2488 | detecting this change (while introducing a race condition if you are not |
1692 | useful simply to find out the new values. |
2489 | the only one changing the path). Can also be useful simply to find out the |
|
|
2490 | new values. |
1693 | |
2491 | |
1694 | =item ev_statdata attr [read-only] |
2492 | =item ev_statdata attr [read-only] |
1695 | |
2493 | |
1696 | The most-recently detected attributes of the file. Although the type is of |
2494 | The most-recently detected attributes of the file. Although the type is |
1697 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
2495 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1698 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
2496 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2497 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1699 | was some error while C<stat>ing the file. |
2498 | some error while C<stat>ing the file. |
1700 | |
2499 | |
1701 | =item ev_statdata prev [read-only] |
2500 | =item ev_statdata prev [read-only] |
1702 | |
2501 | |
1703 | The previous attributes of the file. The callback gets invoked whenever |
2502 | The previous attributes of the file. The callback gets invoked whenever |
1704 | C<prev> != C<attr>. |
2503 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2504 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2505 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1705 | |
2506 | |
1706 | =item ev_tstamp interval [read-only] |
2507 | =item ev_tstamp interval [read-only] |
1707 | |
2508 | |
1708 | The specified interval. |
2509 | The specified interval. |
1709 | |
2510 | |
1710 | =item const char *path [read-only] |
2511 | =item const char *path [read-only] |
1711 | |
2512 | |
1712 | The filesystem path that is being watched. |
2513 | The file system path that is being watched. |
1713 | |
2514 | |
1714 | =back |
2515 | =back |
1715 | |
2516 | |
1716 | =head3 Examples |
2517 | =head3 Examples |
1717 | |
2518 | |
1718 | Example: Watch C</etc/passwd> for attribute changes. |
2519 | Example: Watch C</etc/passwd> for attribute changes. |
1719 | |
2520 | |
1720 | static void |
2521 | static void |
1721 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2522 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1722 | { |
2523 | { |
1723 | /* /etc/passwd changed in some way */ |
2524 | /* /etc/passwd changed in some way */ |
1724 | if (w->attr.st_nlink) |
2525 | if (w->attr.st_nlink) |
1725 | { |
2526 | { |
1726 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2527 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1727 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2528 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1728 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2529 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1729 | } |
2530 | } |
1730 | else |
2531 | else |
1731 | /* you shalt not abuse printf for puts */ |
2532 | /* you shalt not abuse printf for puts */ |
1732 | puts ("wow, /etc/passwd is not there, expect problems. " |
2533 | puts ("wow, /etc/passwd is not there, expect problems. " |
1733 | "if this is windows, they already arrived\n"); |
2534 | "if this is windows, they already arrived\n"); |
1734 | } |
2535 | } |
1735 | |
2536 | |
1736 | ... |
2537 | ... |
1737 | ev_stat passwd; |
2538 | ev_stat passwd; |
1738 | |
2539 | |
1739 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2540 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1740 | ev_stat_start (loop, &passwd); |
2541 | ev_stat_start (loop, &passwd); |
1741 | |
2542 | |
1742 | Example: Like above, but additionally use a one-second delay so we do not |
2543 | Example: Like above, but additionally use a one-second delay so we do not |
1743 | miss updates (however, frequent updates will delay processing, too, so |
2544 | miss updates (however, frequent updates will delay processing, too, so |
1744 | one might do the work both on C<ev_stat> callback invocation I<and> on |
2545 | one might do the work both on C<ev_stat> callback invocation I<and> on |
1745 | C<ev_timer> callback invocation). |
2546 | C<ev_timer> callback invocation). |
1746 | |
2547 | |
1747 | static ev_stat passwd; |
2548 | static ev_stat passwd; |
1748 | static ev_timer timer; |
2549 | static ev_timer timer; |
1749 | |
2550 | |
1750 | static void |
2551 | static void |
1751 | timer_cb (EV_P_ ev_timer *w, int revents) |
2552 | timer_cb (EV_P_ ev_timer *w, int revents) |
1752 | { |
2553 | { |
1753 | ev_timer_stop (EV_A_ w); |
2554 | ev_timer_stop (EV_A_ w); |
1754 | |
2555 | |
1755 | /* now it's one second after the most recent passwd change */ |
2556 | /* now it's one second after the most recent passwd change */ |
1756 | } |
2557 | } |
1757 | |
2558 | |
1758 | static void |
2559 | static void |
1759 | stat_cb (EV_P_ ev_stat *w, int revents) |
2560 | stat_cb (EV_P_ ev_stat *w, int revents) |
1760 | { |
2561 | { |
1761 | /* reset the one-second timer */ |
2562 | /* reset the one-second timer */ |
1762 | ev_timer_again (EV_A_ &timer); |
2563 | ev_timer_again (EV_A_ &timer); |
1763 | } |
2564 | } |
1764 | |
2565 | |
1765 | ... |
2566 | ... |
1766 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2567 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1767 | ev_stat_start (loop, &passwd); |
2568 | ev_stat_start (loop, &passwd); |
1768 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
2569 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1769 | |
2570 | |
1770 | |
2571 | |
1771 | =head2 C<ev_idle> - when you've got nothing better to do... |
2572 | =head2 C<ev_idle> - when you've got nothing better to do... |
1772 | |
2573 | |
1773 | Idle watchers trigger events when no other events of the same or higher |
2574 | Idle watchers trigger events when no other events of the same or higher |
1774 | priority are pending (prepare, check and other idle watchers do not |
2575 | priority are pending (prepare, check and other idle watchers do not count |
1775 | count). |
2576 | as receiving "events"). |
1776 | |
2577 | |
1777 | That is, as long as your process is busy handling sockets or timeouts |
2578 | That is, as long as your process is busy handling sockets or timeouts |
1778 | (or even signals, imagine) of the same or higher priority it will not be |
2579 | (or even signals, imagine) of the same or higher priority it will not be |
1779 | triggered. But when your process is idle (or only lower-priority watchers |
2580 | triggered. But when your process is idle (or only lower-priority watchers |
1780 | are pending), the idle watchers are being called once per event loop |
2581 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1791 | |
2592 | |
1792 | =head3 Watcher-Specific Functions and Data Members |
2593 | =head3 Watcher-Specific Functions and Data Members |
1793 | |
2594 | |
1794 | =over 4 |
2595 | =over 4 |
1795 | |
2596 | |
1796 | =item ev_idle_init (ev_signal *, callback) |
2597 | =item ev_idle_init (ev_idle *, callback) |
1797 | |
2598 | |
1798 | Initialises and configures the idle watcher - it has no parameters of any |
2599 | Initialises and configures the idle watcher - it has no parameters of any |
1799 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2600 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1800 | believe me. |
2601 | believe me. |
1801 | |
2602 | |
… | |
… | |
1804 | =head3 Examples |
2605 | =head3 Examples |
1805 | |
2606 | |
1806 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2607 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1807 | callback, free it. Also, use no error checking, as usual. |
2608 | callback, free it. Also, use no error checking, as usual. |
1808 | |
2609 | |
1809 | static void |
2610 | static void |
1810 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2611 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1811 | { |
2612 | { |
1812 | free (w); |
2613 | free (w); |
1813 | // now do something you wanted to do when the program has |
2614 | // now do something you wanted to do when the program has |
1814 | // no longer anything immediate to do. |
2615 | // no longer anything immediate to do. |
1815 | } |
2616 | } |
1816 | |
2617 | |
1817 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2618 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1818 | ev_idle_init (idle_watcher, idle_cb); |
2619 | ev_idle_init (idle_watcher, idle_cb); |
1819 | ev_idle_start (loop, idle_cb); |
2620 | ev_idle_start (loop, idle_watcher); |
1820 | |
2621 | |
1821 | |
2622 | |
1822 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2623 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1823 | |
2624 | |
1824 | Prepare and check watchers are usually (but not always) used in tandem: |
2625 | Prepare and check watchers are usually (but not always) used in pairs: |
1825 | prepare watchers get invoked before the process blocks and check watchers |
2626 | prepare watchers get invoked before the process blocks and check watchers |
1826 | afterwards. |
2627 | afterwards. |
1827 | |
2628 | |
1828 | You I<must not> call C<ev_loop> or similar functions that enter |
2629 | You I<must not> call C<ev_loop> or similar functions that enter |
1829 | the current event loop from either C<ev_prepare> or C<ev_check> |
2630 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1832 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2633 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1833 | C<ev_check> so if you have one watcher of each kind they will always be |
2634 | C<ev_check> so if you have one watcher of each kind they will always be |
1834 | called in pairs bracketing the blocking call. |
2635 | called in pairs bracketing the blocking call. |
1835 | |
2636 | |
1836 | Their main purpose is to integrate other event mechanisms into libev and |
2637 | Their main purpose is to integrate other event mechanisms into libev and |
1837 | their use is somewhat advanced. This could be used, for example, to track |
2638 | their use is somewhat advanced. They could be used, for example, to track |
1838 | variable changes, implement your own watchers, integrate net-snmp or a |
2639 | variable changes, implement your own watchers, integrate net-snmp or a |
1839 | coroutine library and lots more. They are also occasionally useful if |
2640 | coroutine library and lots more. They are also occasionally useful if |
1840 | you cache some data and want to flush it before blocking (for example, |
2641 | you cache some data and want to flush it before blocking (for example, |
1841 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2642 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1842 | watcher). |
2643 | watcher). |
1843 | |
2644 | |
1844 | This is done by examining in each prepare call which file descriptors need |
2645 | This is done by examining in each prepare call which file descriptors |
1845 | to be watched by the other library, registering C<ev_io> watchers for |
2646 | need to be watched by the other library, registering C<ev_io> watchers |
1846 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2647 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1847 | provide just this functionality). Then, in the check watcher you check for |
2648 | libraries provide exactly this functionality). Then, in the check watcher, |
1848 | any events that occured (by checking the pending status of all watchers |
2649 | you check for any events that occurred (by checking the pending status |
1849 | and stopping them) and call back into the library. The I/O and timer |
2650 | of all watchers and stopping them) and call back into the library. The |
1850 | callbacks will never actually be called (but must be valid nevertheless, |
2651 | I/O and timer callbacks will never actually be called (but must be valid |
1851 | because you never know, you know?). |
2652 | nevertheless, because you never know, you know?). |
1852 | |
2653 | |
1853 | As another example, the Perl Coro module uses these hooks to integrate |
2654 | As another example, the Perl Coro module uses these hooks to integrate |
1854 | coroutines into libev programs, by yielding to other active coroutines |
2655 | coroutines into libev programs, by yielding to other active coroutines |
1855 | during each prepare and only letting the process block if no coroutines |
2656 | during each prepare and only letting the process block if no coroutines |
1856 | are ready to run (it's actually more complicated: it only runs coroutines |
2657 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1859 | loop from blocking if lower-priority coroutines are active, thus mapping |
2660 | loop from blocking if lower-priority coroutines are active, thus mapping |
1860 | low-priority coroutines to idle/background tasks). |
2661 | low-priority coroutines to idle/background tasks). |
1861 | |
2662 | |
1862 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2663 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1863 | priority, to ensure that they are being run before any other watchers |
2664 | priority, to ensure that they are being run before any other watchers |
|
|
2665 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2666 | |
1864 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2667 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1865 | too) should not activate ("feed") events into libev. While libev fully |
2668 | activate ("feed") events into libev. While libev fully supports this, they |
1866 | supports this, they will be called before other C<ev_check> watchers |
2669 | might get executed before other C<ev_check> watchers did their job. As |
1867 | did their job. As C<ev_check> watchers are often used to embed other |
2670 | C<ev_check> watchers are often used to embed other (non-libev) event |
1868 | (non-libev) event loops those other event loops might be in an unusable |
2671 | loops those other event loops might be in an unusable state until their |
1869 | state until their C<ev_check> watcher ran (always remind yourself to |
2672 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1870 | coexist peacefully with others). |
2673 | others). |
1871 | |
2674 | |
1872 | =head3 Watcher-Specific Functions and Data Members |
2675 | =head3 Watcher-Specific Functions and Data Members |
1873 | |
2676 | |
1874 | =over 4 |
2677 | =over 4 |
1875 | |
2678 | |
… | |
… | |
1877 | |
2680 | |
1878 | =item ev_check_init (ev_check *, callback) |
2681 | =item ev_check_init (ev_check *, callback) |
1879 | |
2682 | |
1880 | Initialises and configures the prepare or check watcher - they have no |
2683 | Initialises and configures the prepare or check watcher - they have no |
1881 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2684 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1882 | macros, but using them is utterly, utterly and completely pointless. |
2685 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2686 | pointless. |
1883 | |
2687 | |
1884 | =back |
2688 | =back |
1885 | |
2689 | |
1886 | =head3 Examples |
2690 | =head3 Examples |
1887 | |
2691 | |
1888 | There are a number of principal ways to embed other event loops or modules |
2692 | There are a number of principal ways to embed other event loops or modules |
1889 | into libev. Here are some ideas on how to include libadns into libev |
2693 | into libev. Here are some ideas on how to include libadns into libev |
1890 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
2694 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1891 | use for an actually working example. Another Perl module named C<EV::Glib> |
2695 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1892 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
2696 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1893 | into the Glib event loop). |
2697 | Glib event loop). |
1894 | |
2698 | |
1895 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
2699 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1896 | and in a check watcher, destroy them and call into libadns. What follows |
2700 | and in a check watcher, destroy them and call into libadns. What follows |
1897 | is pseudo-code only of course. This requires you to either use a low |
2701 | is pseudo-code only of course. This requires you to either use a low |
1898 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
2702 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1899 | the callbacks for the IO/timeout watchers might not have been called yet. |
2703 | the callbacks for the IO/timeout watchers might not have been called yet. |
1900 | |
2704 | |
1901 | static ev_io iow [nfd]; |
2705 | static ev_io iow [nfd]; |
1902 | static ev_timer tw; |
2706 | static ev_timer tw; |
1903 | |
2707 | |
1904 | static void |
2708 | static void |
1905 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2709 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1906 | { |
2710 | { |
1907 | } |
2711 | } |
1908 | |
2712 | |
1909 | // create io watchers for each fd and a timer before blocking |
2713 | // create io watchers for each fd and a timer before blocking |
1910 | static void |
2714 | static void |
1911 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2715 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1912 | { |
2716 | { |
1913 | int timeout = 3600000; |
2717 | int timeout = 3600000; |
1914 | struct pollfd fds [nfd]; |
2718 | struct pollfd fds [nfd]; |
1915 | // actual code will need to loop here and realloc etc. |
2719 | // actual code will need to loop here and realloc etc. |
1916 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2720 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1917 | |
2721 | |
1918 | /* the callback is illegal, but won't be called as we stop during check */ |
2722 | /* the callback is illegal, but won't be called as we stop during check */ |
1919 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2723 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1920 | ev_timer_start (loop, &tw); |
2724 | ev_timer_start (loop, &tw); |
1921 | |
2725 | |
1922 | // create one ev_io per pollfd |
2726 | // create one ev_io per pollfd |
1923 | for (int i = 0; i < nfd; ++i) |
2727 | for (int i = 0; i < nfd; ++i) |
1924 | { |
2728 | { |
1925 | ev_io_init (iow + i, io_cb, fds [i].fd, |
2729 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1926 | ((fds [i].events & POLLIN ? EV_READ : 0) |
2730 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1927 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2731 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1928 | |
2732 | |
1929 | fds [i].revents = 0; |
2733 | fds [i].revents = 0; |
1930 | ev_io_start (loop, iow + i); |
2734 | ev_io_start (loop, iow + i); |
1931 | } |
2735 | } |
1932 | } |
2736 | } |
1933 | |
2737 | |
1934 | // stop all watchers after blocking |
2738 | // stop all watchers after blocking |
1935 | static void |
2739 | static void |
1936 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2740 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1937 | { |
2741 | { |
1938 | ev_timer_stop (loop, &tw); |
2742 | ev_timer_stop (loop, &tw); |
1939 | |
2743 | |
1940 | for (int i = 0; i < nfd; ++i) |
2744 | for (int i = 0; i < nfd; ++i) |
1941 | { |
2745 | { |
1942 | // set the relevant poll flags |
2746 | // set the relevant poll flags |
1943 | // could also call adns_processreadable etc. here |
2747 | // could also call adns_processreadable etc. here |
1944 | struct pollfd *fd = fds + i; |
2748 | struct pollfd *fd = fds + i; |
1945 | int revents = ev_clear_pending (iow + i); |
2749 | int revents = ev_clear_pending (iow + i); |
1946 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
2750 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1947 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
2751 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1948 | |
2752 | |
1949 | // now stop the watcher |
2753 | // now stop the watcher |
1950 | ev_io_stop (loop, iow + i); |
2754 | ev_io_stop (loop, iow + i); |
1951 | } |
2755 | } |
1952 | |
2756 | |
1953 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2757 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1954 | } |
2758 | } |
1955 | |
2759 | |
1956 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
2760 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
1957 | in the prepare watcher and would dispose of the check watcher. |
2761 | in the prepare watcher and would dispose of the check watcher. |
1958 | |
2762 | |
1959 | Method 3: If the module to be embedded supports explicit event |
2763 | Method 3: If the module to be embedded supports explicit event |
1960 | notification (adns does), you can also make use of the actual watcher |
2764 | notification (libadns does), you can also make use of the actual watcher |
1961 | callbacks, and only destroy/create the watchers in the prepare watcher. |
2765 | callbacks, and only destroy/create the watchers in the prepare watcher. |
1962 | |
2766 | |
1963 | static void |
2767 | static void |
1964 | timer_cb (EV_P_ ev_timer *w, int revents) |
2768 | timer_cb (EV_P_ ev_timer *w, int revents) |
1965 | { |
2769 | { |
1966 | adns_state ads = (adns_state)w->data; |
2770 | adns_state ads = (adns_state)w->data; |
1967 | update_now (EV_A); |
2771 | update_now (EV_A); |
1968 | |
2772 | |
1969 | adns_processtimeouts (ads, &tv_now); |
2773 | adns_processtimeouts (ads, &tv_now); |
1970 | } |
2774 | } |
1971 | |
2775 | |
1972 | static void |
2776 | static void |
1973 | io_cb (EV_P_ ev_io *w, int revents) |
2777 | io_cb (EV_P_ ev_io *w, int revents) |
1974 | { |
2778 | { |
1975 | adns_state ads = (adns_state)w->data; |
2779 | adns_state ads = (adns_state)w->data; |
1976 | update_now (EV_A); |
2780 | update_now (EV_A); |
1977 | |
2781 | |
1978 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
2782 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
1979 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
2783 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
1980 | } |
2784 | } |
1981 | |
2785 | |
1982 | // do not ever call adns_afterpoll |
2786 | // do not ever call adns_afterpoll |
1983 | |
2787 | |
1984 | Method 4: Do not use a prepare or check watcher because the module you |
2788 | Method 4: Do not use a prepare or check watcher because the module you |
1985 | want to embed is too inflexible to support it. Instead, youc na override |
2789 | want to embed is not flexible enough to support it. Instead, you can |
1986 | their poll function. The drawback with this solution is that the main |
2790 | override their poll function. The drawback with this solution is that the |
1987 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2791 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
1988 | this. |
2792 | this approach, effectively embedding EV as a client into the horrible |
|
|
2793 | libglib event loop. |
1989 | |
2794 | |
1990 | static gint |
2795 | static gint |
1991 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2796 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
1992 | { |
2797 | { |
1993 | int got_events = 0; |
2798 | int got_events = 0; |
1994 | |
2799 | |
1995 | for (n = 0; n < nfds; ++n) |
2800 | for (n = 0; n < nfds; ++n) |
1996 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2801 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
1997 | |
2802 | |
1998 | if (timeout >= 0) |
2803 | if (timeout >= 0) |
1999 | // create/start timer |
2804 | // create/start timer |
2000 | |
2805 | |
2001 | // poll |
2806 | // poll |
2002 | ev_loop (EV_A_ 0); |
2807 | ev_loop (EV_A_ 0); |
2003 | |
2808 | |
2004 | // stop timer again |
2809 | // stop timer again |
2005 | if (timeout >= 0) |
2810 | if (timeout >= 0) |
2006 | ev_timer_stop (EV_A_ &to); |
2811 | ev_timer_stop (EV_A_ &to); |
2007 | |
2812 | |
2008 | // stop io watchers again - their callbacks should have set |
2813 | // stop io watchers again - their callbacks should have set |
2009 | for (n = 0; n < nfds; ++n) |
2814 | for (n = 0; n < nfds; ++n) |
2010 | ev_io_stop (EV_A_ iow [n]); |
2815 | ev_io_stop (EV_A_ iow [n]); |
2011 | |
2816 | |
2012 | return got_events; |
2817 | return got_events; |
2013 | } |
2818 | } |
2014 | |
2819 | |
2015 | |
2820 | |
2016 | =head2 C<ev_embed> - when one backend isn't enough... |
2821 | =head2 C<ev_embed> - when one backend isn't enough... |
2017 | |
2822 | |
2018 | This is a rather advanced watcher type that lets you embed one event loop |
2823 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
2024 | prioritise I/O. |
2829 | prioritise I/O. |
2025 | |
2830 | |
2026 | As an example for a bug workaround, the kqueue backend might only support |
2831 | As an example for a bug workaround, the kqueue backend might only support |
2027 | sockets on some platform, so it is unusable as generic backend, but you |
2832 | sockets on some platform, so it is unusable as generic backend, but you |
2028 | still want to make use of it because you have many sockets and it scales |
2833 | still want to make use of it because you have many sockets and it scales |
2029 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2834 | so nicely. In this case, you would create a kqueue-based loop and embed |
2030 | into your default loop (which might use e.g. poll). Overall operation will |
2835 | it into your default loop (which might use e.g. poll). Overall operation |
2031 | be a bit slower because first libev has to poll and then call kevent, but |
2836 | will be a bit slower because first libev has to call C<poll> and then |
2032 | at least you can use both at what they are best. |
2837 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2838 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2033 | |
2839 | |
2034 | As for prioritising I/O: rarely you have the case where some fds have |
2840 | As for prioritising I/O: under rare circumstances you have the case where |
2035 | to be watched and handled very quickly (with low latency), and even |
2841 | some fds have to be watched and handled very quickly (with low latency), |
2036 | priorities and idle watchers might have too much overhead. In this case |
2842 | and even priorities and idle watchers might have too much overhead. In |
2037 | you would put all the high priority stuff in one loop and all the rest in |
2843 | this case you would put all the high priority stuff in one loop and all |
2038 | a second one, and embed the second one in the first. |
2844 | the rest in a second one, and embed the second one in the first. |
2039 | |
2845 | |
2040 | As long as the watcher is active, the callback will be invoked every time |
2846 | As long as the watcher is active, the callback will be invoked every |
2041 | there might be events pending in the embedded loop. The callback must then |
2847 | time there might be events pending in the embedded loop. The callback |
2042 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2848 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2043 | their callbacks (you could also start an idle watcher to give the embedded |
2849 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2044 | loop strictly lower priority for example). You can also set the callback |
2850 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2045 | to C<0>, in which case the embed watcher will automatically execute the |
2851 | to give the embedded loop strictly lower priority for example). |
2046 | embedded loop sweep. |
|
|
2047 | |
2852 | |
2048 | As long as the watcher is started it will automatically handle events. The |
2853 | You can also set the callback to C<0>, in which case the embed watcher |
2049 | callback will be invoked whenever some events have been handled. You can |
2854 | will automatically execute the embedded loop sweep whenever necessary. |
2050 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2051 | interested in that. |
|
|
2052 | |
2855 | |
2053 | Also, there have not currently been made special provisions for forking: |
2856 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2054 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2857 | is active, i.e., the embedded loop will automatically be forked when the |
2055 | but you will also have to stop and restart any C<ev_embed> watchers |
2858 | embedding loop forks. In other cases, the user is responsible for calling |
2056 | yourself. |
2859 | C<ev_loop_fork> on the embedded loop. |
2057 | |
2860 | |
2058 | Unfortunately, not all backends are embeddable, only the ones returned by |
2861 | Unfortunately, not all backends are embeddable: only the ones returned by |
2059 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2862 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2060 | portable one. |
2863 | portable one. |
2061 | |
2864 | |
2062 | So when you want to use this feature you will always have to be prepared |
2865 | So when you want to use this feature you will always have to be prepared |
2063 | that you cannot get an embeddable loop. The recommended way to get around |
2866 | that you cannot get an embeddable loop. The recommended way to get around |
2064 | this is to have a separate variables for your embeddable loop, try to |
2867 | this is to have a separate variables for your embeddable loop, try to |
2065 | create it, and if that fails, use the normal loop for everything. |
2868 | create it, and if that fails, use the normal loop for everything. |
2066 | |
2869 | |
|
|
2870 | =head3 C<ev_embed> and fork |
|
|
2871 | |
|
|
2872 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2873 | automatically be applied to the embedded loop as well, so no special |
|
|
2874 | fork handling is required in that case. When the watcher is not running, |
|
|
2875 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2876 | as applicable. |
|
|
2877 | |
2067 | =head3 Watcher-Specific Functions and Data Members |
2878 | =head3 Watcher-Specific Functions and Data Members |
2068 | |
2879 | |
2069 | =over 4 |
2880 | =over 4 |
2070 | |
2881 | |
2071 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2882 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
2074 | |
2885 | |
2075 | Configures the watcher to embed the given loop, which must be |
2886 | Configures the watcher to embed the given loop, which must be |
2076 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2887 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2077 | invoked automatically, otherwise it is the responsibility of the callback |
2888 | invoked automatically, otherwise it is the responsibility of the callback |
2078 | to invoke it (it will continue to be called until the sweep has been done, |
2889 | to invoke it (it will continue to be called until the sweep has been done, |
2079 | if you do not want thta, you need to temporarily stop the embed watcher). |
2890 | if you do not want that, you need to temporarily stop the embed watcher). |
2080 | |
2891 | |
2081 | =item ev_embed_sweep (loop, ev_embed *) |
2892 | =item ev_embed_sweep (loop, ev_embed *) |
2082 | |
2893 | |
2083 | Make a single, non-blocking sweep over the embedded loop. This works |
2894 | Make a single, non-blocking sweep over the embedded loop. This works |
2084 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2895 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2085 | apropriate way for embedded loops. |
2896 | appropriate way for embedded loops. |
2086 | |
2897 | |
2087 | =item struct ev_loop *other [read-only] |
2898 | =item struct ev_loop *other [read-only] |
2088 | |
2899 | |
2089 | The embedded event loop. |
2900 | The embedded event loop. |
2090 | |
2901 | |
… | |
… | |
2092 | |
2903 | |
2093 | =head3 Examples |
2904 | =head3 Examples |
2094 | |
2905 | |
2095 | Example: Try to get an embeddable event loop and embed it into the default |
2906 | Example: Try to get an embeddable event loop and embed it into the default |
2096 | event loop. If that is not possible, use the default loop. The default |
2907 | event loop. If that is not possible, use the default loop. The default |
2097 | loop is stored in C<loop_hi>, while the mebeddable loop is stored in |
2908 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
2098 | C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be |
2909 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2099 | used). |
2910 | used). |
2100 | |
2911 | |
2101 | struct ev_loop *loop_hi = ev_default_init (0); |
2912 | struct ev_loop *loop_hi = ev_default_init (0); |
2102 | struct ev_loop *loop_lo = 0; |
2913 | struct ev_loop *loop_lo = 0; |
2103 | struct ev_embed embed; |
2914 | ev_embed embed; |
2104 | |
2915 | |
2105 | // see if there is a chance of getting one that works |
2916 | // see if there is a chance of getting one that works |
2106 | // (remember that a flags value of 0 means autodetection) |
2917 | // (remember that a flags value of 0 means autodetection) |
2107 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2918 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2108 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2919 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2109 | : 0; |
2920 | : 0; |
2110 | |
2921 | |
2111 | // if we got one, then embed it, otherwise default to loop_hi |
2922 | // if we got one, then embed it, otherwise default to loop_hi |
2112 | if (loop_lo) |
2923 | if (loop_lo) |
2113 | { |
2924 | { |
2114 | ev_embed_init (&embed, 0, loop_lo); |
2925 | ev_embed_init (&embed, 0, loop_lo); |
2115 | ev_embed_start (loop_hi, &embed); |
2926 | ev_embed_start (loop_hi, &embed); |
2116 | } |
2927 | } |
2117 | else |
2928 | else |
2118 | loop_lo = loop_hi; |
2929 | loop_lo = loop_hi; |
2119 | |
2930 | |
2120 | Example: Check if kqueue is available but not recommended and create |
2931 | Example: Check if kqueue is available but not recommended and create |
2121 | a kqueue backend for use with sockets (which usually work with any |
2932 | a kqueue backend for use with sockets (which usually work with any |
2122 | kqueue implementation). Store the kqueue/socket-only event loop in |
2933 | kqueue implementation). Store the kqueue/socket-only event loop in |
2123 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2934 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2124 | |
2935 | |
2125 | struct ev_loop *loop = ev_default_init (0); |
2936 | struct ev_loop *loop = ev_default_init (0); |
2126 | struct ev_loop *loop_socket = 0; |
2937 | struct ev_loop *loop_socket = 0; |
2127 | struct ev_embed embed; |
2938 | ev_embed embed; |
2128 | |
2939 | |
2129 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2940 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2130 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2941 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2131 | { |
2942 | { |
2132 | ev_embed_init (&embed, 0, loop_socket); |
2943 | ev_embed_init (&embed, 0, loop_socket); |
2133 | ev_embed_start (loop, &embed); |
2944 | ev_embed_start (loop, &embed); |
2134 | } |
2945 | } |
2135 | |
2946 | |
2136 | if (!loop_socket) |
2947 | if (!loop_socket) |
2137 | loop_socket = loop; |
2948 | loop_socket = loop; |
2138 | |
2949 | |
2139 | // now use loop_socket for all sockets, and loop for everything else |
2950 | // now use loop_socket for all sockets, and loop for everything else |
2140 | |
2951 | |
2141 | |
2952 | |
2142 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2953 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2143 | |
2954 | |
2144 | Fork watchers are called when a C<fork ()> was detected (usually because |
2955 | Fork watchers are called when a C<fork ()> was detected (usually because |
… | |
… | |
2147 | event loop blocks next and before C<ev_check> watchers are being called, |
2958 | event loop blocks next and before C<ev_check> watchers are being called, |
2148 | and only in the child after the fork. If whoever good citizen calling |
2959 | and only in the child after the fork. If whoever good citizen calling |
2149 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2960 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2150 | handlers will be invoked, too, of course. |
2961 | handlers will be invoked, too, of course. |
2151 | |
2962 | |
|
|
2963 | =head3 The special problem of life after fork - how is it possible? |
|
|
2964 | |
|
|
2965 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2966 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2967 | sequence should be handled by libev without any problems. |
|
|
2968 | |
|
|
2969 | 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 |
|
|
2971 | fork. |
|
|
2972 | |
|
|
2973 | The default mode of operation (for libev, with application help to detect |
|
|
2974 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2975 | when I<either> the parent I<or> the child process continues. |
|
|
2976 | |
|
|
2977 | When both processes want to continue using libev, then this is usually the |
|
|
2978 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2979 | supposed to continue with all watchers in place as before, while the other |
|
|
2980 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2981 | |
|
|
2982 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2983 | simply create a new event loop, which of course will be "empty", and |
|
|
2984 | use that for new watchers. This has the advantage of not touching more |
|
|
2985 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2986 | disadvantage of having to use multiple event loops (which do not support |
|
|
2987 | signal watchers). |
|
|
2988 | |
|
|
2989 | 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 |
|
|
2991 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2992 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2993 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2994 | also that in that case, you have to re-register any signal watchers. |
|
|
2995 | |
2152 | =head3 Watcher-Specific Functions and Data Members |
2996 | =head3 Watcher-Specific Functions and Data Members |
2153 | |
2997 | |
2154 | =over 4 |
2998 | =over 4 |
2155 | |
2999 | |
2156 | =item ev_fork_init (ev_signal *, callback) |
3000 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2185 | =head3 Queueing |
3029 | =head3 Queueing |
2186 | |
3030 | |
2187 | C<ev_async> does not support queueing of data in any way. The reason |
3031 | C<ev_async> does not support queueing of data in any way. The reason |
2188 | is that the author does not know of a simple (or any) algorithm for a |
3032 | is that the author does not know of a simple (or any) algorithm for a |
2189 | multiple-writer-single-reader queue that works in all cases and doesn't |
3033 | multiple-writer-single-reader queue that works in all cases and doesn't |
2190 | need elaborate support such as pthreads. |
3034 | need elaborate support such as pthreads or unportable memory access |
|
|
3035 | semantics. |
2191 | |
3036 | |
2192 | That means that if you want to queue data, you have to provide your own |
3037 | That means that if you want to queue data, you have to provide your own |
2193 | queue. But at least I can tell you would implement locking around your |
3038 | queue. But at least I can tell you how to implement locking around your |
2194 | queue: |
3039 | queue: |
2195 | |
3040 | |
2196 | =over 4 |
3041 | =over 4 |
2197 | |
3042 | |
2198 | =item queueing from a signal handler context |
3043 | =item queueing from a signal handler context |
2199 | |
3044 | |
2200 | To implement race-free queueing, you simply add to the queue in the signal |
3045 | To implement race-free queueing, you simply add to the queue in the signal |
2201 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3046 | handler but you block the signal handler in the watcher callback. Here is |
2202 | some fictitiuous SIGUSR1 handler: |
3047 | an example that does that for some fictitious SIGUSR1 handler: |
2203 | |
3048 | |
2204 | static ev_async mysig; |
3049 | static ev_async mysig; |
2205 | |
3050 | |
2206 | static void |
3051 | static void |
2207 | sigusr1_handler (void) |
3052 | sigusr1_handler (void) |
… | |
… | |
2273 | =over 4 |
3118 | =over 4 |
2274 | |
3119 | |
2275 | =item ev_async_init (ev_async *, callback) |
3120 | =item ev_async_init (ev_async *, callback) |
2276 | |
3121 | |
2277 | Initialises and configures the async watcher - it has no parameters of any |
3122 | Initialises and configures the async watcher - it has no parameters of any |
2278 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3123 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2279 | believe me. |
3124 | trust me. |
2280 | |
3125 | |
2281 | =item ev_async_send (loop, ev_async *) |
3126 | =item ev_async_send (loop, ev_async *) |
2282 | |
3127 | |
2283 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3128 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2284 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3129 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2285 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3130 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2286 | similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding |
3131 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2287 | section below on what exactly this means). |
3132 | section below on what exactly this means). |
2288 | |
3133 | |
|
|
3134 | 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 |
|
|
3136 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3137 | reset when the event loop detects that). |
|
|
3138 | |
2289 | This call incurs the overhead of a syscall only once per loop iteration, |
3139 | This call incurs the overhead of a system call only once per event loop |
2290 | so while the overhead might be noticable, it doesn't apply to repeated |
3140 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2291 | calls to C<ev_async_send>. |
3141 | repeated calls to C<ev_async_send> for the same event loop. |
2292 | |
3142 | |
2293 | =item bool = ev_async_pending (ev_async *) |
3143 | =item bool = ev_async_pending (ev_async *) |
2294 | |
3144 | |
2295 | Returns a non-zero value when C<ev_async_send> has been called on the |
3145 | Returns a non-zero value when C<ev_async_send> has been called on the |
2296 | watcher but the event has not yet been processed (or even noted) by the |
3146 | watcher but the event has not yet been processed (or even noted) by the |
2297 | event loop. |
3147 | event loop. |
2298 | |
3148 | |
2299 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3149 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2300 | the loop iterates next and checks for the watcher to have become active, |
3150 | the loop iterates next and checks for the watcher to have become active, |
2301 | it will reset the flag again. C<ev_async_pending> can be used to very |
3151 | it will reset the flag again. C<ev_async_pending> can be used to very |
2302 | quickly check wether invoking the loop might be a good idea. |
3152 | quickly check whether invoking the loop might be a good idea. |
2303 | |
3153 | |
2304 | Not that this does I<not> check wether the watcher itself is pending, only |
3154 | Not that this does I<not> check whether the watcher itself is pending, |
2305 | wether it has been requested to make this watcher pending. |
3155 | only whether it has been requested to make this watcher pending: there |
|
|
3156 | is a time window between the event loop checking and resetting the async |
|
|
3157 | notification, and the callback being invoked. |
2306 | |
3158 | |
2307 | =back |
3159 | =back |
2308 | |
3160 | |
2309 | |
3161 | |
2310 | =head1 OTHER FUNCTIONS |
3162 | =head1 OTHER FUNCTIONS |
… | |
… | |
2314 | =over 4 |
3166 | =over 4 |
2315 | |
3167 | |
2316 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3168 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2317 | |
3169 | |
2318 | This function combines a simple timer and an I/O watcher, calls your |
3170 | This function combines a simple timer and an I/O watcher, calls your |
2319 | callback on whichever event happens first and automatically stop both |
3171 | callback on whichever event happens first and automatically stops both |
2320 | watchers. This is useful if you want to wait for a single event on an fd |
3172 | watchers. This is useful if you want to wait for a single event on an fd |
2321 | or timeout without having to allocate/configure/start/stop/free one or |
3173 | or timeout without having to allocate/configure/start/stop/free one or |
2322 | more watchers yourself. |
3174 | more watchers yourself. |
2323 | |
3175 | |
2324 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3176 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2325 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3177 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2326 | C<events> set will be craeted and started. |
3178 | the given C<fd> and C<events> set will be created and started. |
2327 | |
3179 | |
2328 | If C<timeout> is less than 0, then no timeout watcher will be |
3180 | If C<timeout> is less than 0, then no timeout watcher will be |
2329 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3181 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2330 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3182 | repeat = 0) will be started. C<0> is a valid timeout. |
2331 | dubious value. |
|
|
2332 | |
3183 | |
2333 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3184 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2334 | passed an C<revents> set like normal event callbacks (a combination of |
3185 | passed an C<revents> set like normal event callbacks (a combination of |
2335 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3186 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2336 | value passed to C<ev_once>: |
3187 | 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 |
|
|
3189 | events precedence. |
2337 | |
3190 | |
|
|
3191 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
3192 | |
2338 | static void stdin_ready (int revents, void *arg) |
3193 | static void stdin_ready (int revents, void *arg) |
2339 | { |
3194 | { |
2340 | if (revents & EV_TIMEOUT) |
|
|
2341 | /* doh, nothing entered */; |
|
|
2342 | else if (revents & EV_READ) |
3195 | if (revents & EV_READ) |
2343 | /* stdin might have data for us, joy! */; |
3196 | /* stdin might have data for us, joy! */; |
|
|
3197 | else if (revents & EV_TIMEOUT) |
|
|
3198 | /* doh, nothing entered */; |
2344 | } |
3199 | } |
2345 | |
3200 | |
2346 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3201 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2347 | |
3202 | |
2348 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2349 | |
|
|
2350 | Feeds the given event set into the event loop, as if the specified event |
|
|
2351 | had happened for the specified watcher (which must be a pointer to an |
|
|
2352 | initialised but not necessarily started event watcher). |
|
|
2353 | |
|
|
2354 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3203 | =item ev_feed_fd_event (loop, int fd, int revents) |
2355 | |
3204 | |
2356 | Feed an event on the given fd, as if a file descriptor backend detected |
3205 | Feed an event on the given fd, as if a file descriptor backend detected |
2357 | the given events it. |
3206 | the given events it. |
2358 | |
3207 | |
2359 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3208 | =item ev_feed_signal_event (loop, int signum) |
2360 | |
3209 | |
2361 | Feed an event as if the given signal occured (C<loop> must be the default |
3210 | Feed an event as if the given signal occurred (C<loop> must be the default |
2362 | loop!). |
3211 | loop!). |
2363 | |
3212 | |
2364 | =back |
3213 | =back |
2365 | |
3214 | |
2366 | |
3215 | |
… | |
… | |
2382 | |
3231 | |
2383 | =item * Priorities are not currently supported. Initialising priorities |
3232 | =item * Priorities are not currently supported. Initialising priorities |
2384 | will fail and all watchers will have the same priority, even though there |
3233 | will fail and all watchers will have the same priority, even though there |
2385 | is an ev_pri field. |
3234 | is an ev_pri field. |
2386 | |
3235 | |
|
|
3236 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
3237 | first base created (== the default loop) gets the signals. |
|
|
3238 | |
2387 | =item * Other members are not supported. |
3239 | =item * Other members are not supported. |
2388 | |
3240 | |
2389 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3241 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2390 | to use the libev header file and library. |
3242 | to use the libev header file and library. |
2391 | |
3243 | |
2392 | =back |
3244 | =back |
2393 | |
3245 | |
2394 | =head1 C++ SUPPORT |
3246 | =head1 C++ SUPPORT |
2395 | |
3247 | |
2396 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3248 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2397 | you to use some convinience methods to start/stop watchers and also change |
3249 | you to use some convenience methods to start/stop watchers and also change |
2398 | the callback model to a model using method callbacks on objects. |
3250 | the callback model to a model using method callbacks on objects. |
2399 | |
3251 | |
2400 | To use it, |
3252 | To use it, |
2401 | |
3253 | |
2402 | #include <ev++.h> |
3254 | #include <ev++.h> |
2403 | |
3255 | |
2404 | This automatically includes F<ev.h> and puts all of its definitions (many |
3256 | This automatically includes F<ev.h> and puts all of its definitions (many |
2405 | of them macros) into the global namespace. All C++ specific things are |
3257 | of them macros) into the global namespace. All C++ specific things are |
2406 | put into the C<ev> namespace. It should support all the same embedding |
3258 | put into the C<ev> namespace. It should support all the same embedding |
2407 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
3259 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
2441 | |
3293 | |
2442 | =over 4 |
3294 | =over 4 |
2443 | |
3295 | |
2444 | =item ev::TYPE::TYPE () |
3296 | =item ev::TYPE::TYPE () |
2445 | |
3297 | |
2446 | =item ev::TYPE::TYPE (struct ev_loop *) |
3298 | =item ev::TYPE::TYPE (loop) |
2447 | |
3299 | |
2448 | =item ev::TYPE::~TYPE |
3300 | =item ev::TYPE::~TYPE |
2449 | |
3301 | |
2450 | The constructor (optionally) takes an event loop to associate the watcher |
3302 | The constructor (optionally) takes an event loop to associate the watcher |
2451 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3303 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2474 | your compiler is good :), then the method will be fully inlined into the |
3326 | your compiler is good :), then the method will be fully inlined into the |
2475 | thunking function, making it as fast as a direct C callback. |
3327 | thunking function, making it as fast as a direct C callback. |
2476 | |
3328 | |
2477 | Example: simple class declaration and watcher initialisation |
3329 | Example: simple class declaration and watcher initialisation |
2478 | |
3330 | |
2479 | struct myclass |
3331 | struct myclass |
2480 | { |
3332 | { |
2481 | void io_cb (ev::io &w, int revents) { } |
3333 | void io_cb (ev::io &w, int revents) { } |
2482 | } |
3334 | } |
2483 | |
3335 | |
2484 | myclass obj; |
3336 | myclass obj; |
2485 | ev::io iow; |
3337 | ev::io iow; |
2486 | iow.set <myclass, &myclass::io_cb> (&obj); |
3338 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3339 | |
|
|
3340 | =item w->set (object *) |
|
|
3341 | |
|
|
3342 | This is an B<experimental> feature that might go away in a future version. |
|
|
3343 | |
|
|
3344 | 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 |
|
|
3346 | functor objects without having to manually specify the C<operator ()> all |
|
|
3347 | the time. Incidentally, you can then also leave out the template argument |
|
|
3348 | list. |
|
|
3349 | |
|
|
3350 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3351 | int revents)>. |
|
|
3352 | |
|
|
3353 | See the method-C<set> above for more details. |
|
|
3354 | |
|
|
3355 | Example: use a functor object as callback. |
|
|
3356 | |
|
|
3357 | struct myfunctor |
|
|
3358 | { |
|
|
3359 | void operator() (ev::io &w, int revents) |
|
|
3360 | { |
|
|
3361 | ... |
|
|
3362 | } |
|
|
3363 | } |
|
|
3364 | |
|
|
3365 | myfunctor f; |
|
|
3366 | |
|
|
3367 | ev::io w; |
|
|
3368 | w.set (&f); |
2487 | |
3369 | |
2488 | =item w->set<function> (void *data = 0) |
3370 | =item w->set<function> (void *data = 0) |
2489 | |
3371 | |
2490 | Also sets a callback, but uses a static method or plain function as |
3372 | Also sets a callback, but uses a static method or plain function as |
2491 | callback. The optional C<data> argument will be stored in the watcher's |
3373 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2493 | |
3375 | |
2494 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3376 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2495 | |
3377 | |
2496 | See the method-C<set> above for more details. |
3378 | See the method-C<set> above for more details. |
2497 | |
3379 | |
2498 | Example: |
3380 | Example: Use a plain function as callback. |
2499 | |
3381 | |
2500 | static void io_cb (ev::io &w, int revents) { } |
3382 | static void io_cb (ev::io &w, int revents) { } |
2501 | iow.set <io_cb> (); |
3383 | iow.set <io_cb> (); |
2502 | |
3384 | |
2503 | =item w->set (struct ev_loop *) |
3385 | =item w->set (loop) |
2504 | |
3386 | |
2505 | Associates a different C<struct ev_loop> with this watcher. You can only |
3387 | Associates a different C<struct ev_loop> with this watcher. You can only |
2506 | do this when the watcher is inactive (and not pending either). |
3388 | do this when the watcher is inactive (and not pending either). |
2507 | |
3389 | |
2508 | =item w->set ([args]) |
3390 | =item w->set ([arguments]) |
2509 | |
3391 | |
2510 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
3392 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
2511 | called at least once. Unlike the C counterpart, an active watcher gets |
3393 | called at least once. Unlike the C counterpart, an active watcher gets |
2512 | automatically stopped and restarted when reconfiguring it with this |
3394 | automatically stopped and restarted when reconfiguring it with this |
2513 | method. |
3395 | method. |
2514 | |
3396 | |
2515 | =item w->start () |
3397 | =item w->start () |
… | |
… | |
2539 | =back |
3421 | =back |
2540 | |
3422 | |
2541 | Example: Define a class with an IO and idle watcher, start one of them in |
3423 | Example: Define a class with an IO and idle watcher, start one of them in |
2542 | the constructor. |
3424 | the constructor. |
2543 | |
3425 | |
2544 | class myclass |
3426 | class myclass |
2545 | { |
3427 | { |
2546 | ev::io io; void io_cb (ev::io &w, int revents); |
3428 | ev::io io ; void io_cb (ev::io &w, int revents); |
2547 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3429 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2548 | |
3430 | |
2549 | myclass (int fd) |
3431 | myclass (int fd) |
2550 | { |
3432 | { |
2551 | io .set <myclass, &myclass::io_cb > (this); |
3433 | io .set <myclass, &myclass::io_cb > (this); |
2552 | idle.set <myclass, &myclass::idle_cb> (this); |
3434 | idle.set <myclass, &myclass::idle_cb> (this); |
2553 | |
3435 | |
2554 | io.start (fd, ev::READ); |
3436 | io.start (fd, ev::READ); |
2555 | } |
3437 | } |
2556 | }; |
3438 | }; |
2557 | |
3439 | |
2558 | |
3440 | |
2559 | =head1 OTHER LANGUAGE BINDINGS |
3441 | =head1 OTHER LANGUAGE BINDINGS |
2560 | |
3442 | |
2561 | Libev does not offer other language bindings itself, but bindings for a |
3443 | Libev does not offer other language bindings itself, but bindings for a |
2562 | numbe rof languages exist in the form of third-party packages. If you know |
3444 | number of languages exist in the form of third-party packages. If you know |
2563 | any interesting language binding in addition to the ones listed here, drop |
3445 | any interesting language binding in addition to the ones listed here, drop |
2564 | me a note. |
3446 | me a note. |
2565 | |
3447 | |
2566 | =over 4 |
3448 | =over 4 |
2567 | |
3449 | |
2568 | =item Perl |
3450 | =item Perl |
2569 | |
3451 | |
2570 | The EV module implements the full libev API and is actually used to test |
3452 | The EV module implements the full libev API and is actually used to test |
2571 | libev. EV is developed together with libev. Apart from the EV core module, |
3453 | libev. EV is developed together with libev. Apart from the EV core module, |
2572 | there are additional modules that implement libev-compatible interfaces |
3454 | there are additional modules that implement libev-compatible interfaces |
2573 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3455 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2574 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3456 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3457 | and C<EV::Glib>). |
2575 | |
3458 | |
2576 | It can be found and installed via CPAN, its homepage is found at |
3459 | It can be found and installed via CPAN, its homepage is at |
2577 | L<http://software.schmorp.de/pkg/EV>. |
3460 | L<http://software.schmorp.de/pkg/EV>. |
2578 | |
3461 | |
|
|
3462 | =item Python |
|
|
3463 | |
|
|
3464 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
3465 | seems to be quite complete and well-documented. |
|
|
3466 | |
2579 | =item Ruby |
3467 | =item Ruby |
2580 | |
3468 | |
2581 | Tony Arcieri has written a ruby extension that offers access to a subset |
3469 | Tony Arcieri has written a ruby extension that offers access to a subset |
2582 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
3470 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2583 | more on top of it. It can be found via gem servers. Its homepage is at |
3471 | more on top of it. It can be found via gem servers. Its homepage is at |
2584 | L<http://rev.rubyforge.org/>. |
3472 | L<http://rev.rubyforge.org/>. |
2585 | |
3473 | |
|
|
3474 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3475 | makes rev work even on mingw. |
|
|
3476 | |
|
|
3477 | =item Haskell |
|
|
3478 | |
|
|
3479 | A haskell binding to libev is available at |
|
|
3480 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3481 | |
2586 | =item D |
3482 | =item D |
2587 | |
3483 | |
2588 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3484 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2589 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
3485 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3486 | |
|
|
3487 | =item Ocaml |
|
|
3488 | |
|
|
3489 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3490 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3491 | |
|
|
3492 | =item Lua |
|
|
3493 | |
|
|
3494 | 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 |
|
|
3496 | L<http://github.com/brimworks/lua-ev>. |
2590 | |
3497 | |
2591 | =back |
3498 | =back |
2592 | |
3499 | |
2593 | |
3500 | |
2594 | =head1 MACRO MAGIC |
3501 | =head1 MACRO MAGIC |
2595 | |
3502 | |
2596 | Libev can be compiled with a variety of options, the most fundamantal |
3503 | Libev can be compiled with a variety of options, the most fundamental |
2597 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
3504 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2598 | functions and callbacks have an initial C<struct ev_loop *> argument. |
3505 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2599 | |
3506 | |
2600 | To make it easier to write programs that cope with either variant, the |
3507 | To make it easier to write programs that cope with either variant, the |
2601 | following macros are defined: |
3508 | following macros are defined: |
… | |
… | |
2606 | |
3513 | |
2607 | This provides the loop I<argument> for functions, if one is required ("ev |
3514 | This provides the loop I<argument> for functions, if one is required ("ev |
2608 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3515 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2609 | C<EV_A_> is used when other arguments are following. Example: |
3516 | C<EV_A_> is used when other arguments are following. Example: |
2610 | |
3517 | |
2611 | ev_unref (EV_A); |
3518 | ev_unref (EV_A); |
2612 | ev_timer_add (EV_A_ watcher); |
3519 | ev_timer_add (EV_A_ watcher); |
2613 | ev_loop (EV_A_ 0); |
3520 | ev_loop (EV_A_ 0); |
2614 | |
3521 | |
2615 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3522 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2616 | which is often provided by the following macro. |
3523 | which is often provided by the following macro. |
2617 | |
3524 | |
2618 | =item C<EV_P>, C<EV_P_> |
3525 | =item C<EV_P>, C<EV_P_> |
2619 | |
3526 | |
2620 | This provides the loop I<parameter> for functions, if one is required ("ev |
3527 | This provides the loop I<parameter> for functions, if one is required ("ev |
2621 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
3528 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
2622 | C<EV_P_> is used when other parameters are following. Example: |
3529 | C<EV_P_> is used when other parameters are following. Example: |
2623 | |
3530 | |
2624 | // this is how ev_unref is being declared |
3531 | // this is how ev_unref is being declared |
2625 | static void ev_unref (EV_P); |
3532 | static void ev_unref (EV_P); |
2626 | |
3533 | |
2627 | // this is how you can declare your typical callback |
3534 | // this is how you can declare your typical callback |
2628 | static void cb (EV_P_ ev_timer *w, int revents) |
3535 | static void cb (EV_P_ ev_timer *w, int revents) |
2629 | |
3536 | |
2630 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
3537 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
2631 | suitable for use with C<EV_A>. |
3538 | suitable for use with C<EV_A>. |
2632 | |
3539 | |
2633 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3540 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2634 | |
3541 | |
2635 | Similar to the other two macros, this gives you the value of the default |
3542 | Similar to the other two macros, this gives you the value of the default |
2636 | loop, if multiple loops are supported ("ev loop default"). |
3543 | loop, if multiple loops are supported ("ev loop default"). |
|
|
3544 | |
|
|
3545 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
3546 | |
|
|
3547 | 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 |
|
|
3549 | is undefined when the default loop has not been initialised by a previous |
|
|
3550 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
3551 | |
|
|
3552 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
3553 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2637 | |
3554 | |
2638 | =back |
3555 | =back |
2639 | |
3556 | |
2640 | Example: Declare and initialise a check watcher, utilising the above |
3557 | Example: Declare and initialise a check watcher, utilising the above |
2641 | macros so it will work regardless of whether multiple loops are supported |
3558 | macros so it will work regardless of whether multiple loops are supported |
2642 | or not. |
3559 | or not. |
2643 | |
3560 | |
2644 | static void |
3561 | static void |
2645 | check_cb (EV_P_ ev_timer *w, int revents) |
3562 | check_cb (EV_P_ ev_timer *w, int revents) |
2646 | { |
3563 | { |
2647 | ev_check_stop (EV_A_ w); |
3564 | ev_check_stop (EV_A_ w); |
2648 | } |
3565 | } |
2649 | |
3566 | |
2650 | ev_check check; |
3567 | ev_check check; |
2651 | ev_check_init (&check, check_cb); |
3568 | ev_check_init (&check, check_cb); |
2652 | ev_check_start (EV_DEFAULT_ &check); |
3569 | ev_check_start (EV_DEFAULT_ &check); |
2653 | ev_loop (EV_DEFAULT_ 0); |
3570 | ev_loop (EV_DEFAULT_ 0); |
2654 | |
3571 | |
2655 | =head1 EMBEDDING |
3572 | =head1 EMBEDDING |
2656 | |
3573 | |
2657 | Libev can (and often is) directly embedded into host |
3574 | Libev can (and often is) directly embedded into host |
2658 | applications. Examples of applications that embed it include the Deliantra |
3575 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2665 | libev somewhere in your source tree). |
3582 | libev somewhere in your source tree). |
2666 | |
3583 | |
2667 | =head2 FILESETS |
3584 | =head2 FILESETS |
2668 | |
3585 | |
2669 | Depending on what features you need you need to include one or more sets of files |
3586 | Depending on what features you need you need to include one or more sets of files |
2670 | in your app. |
3587 | in your application. |
2671 | |
3588 | |
2672 | =head3 CORE EVENT LOOP |
3589 | =head3 CORE EVENT LOOP |
2673 | |
3590 | |
2674 | To include only the libev core (all the C<ev_*> functions), with manual |
3591 | To include only the libev core (all the C<ev_*> functions), with manual |
2675 | configuration (no autoconf): |
3592 | configuration (no autoconf): |
2676 | |
3593 | |
2677 | #define EV_STANDALONE 1 |
3594 | #define EV_STANDALONE 1 |
2678 | #include "ev.c" |
3595 | #include "ev.c" |
2679 | |
3596 | |
2680 | This will automatically include F<ev.h>, too, and should be done in a |
3597 | This will automatically include F<ev.h>, too, and should be done in a |
2681 | single C source file only to provide the function implementations. To use |
3598 | single C source file only to provide the function implementations. To use |
2682 | it, do the same for F<ev.h> in all files wishing to use this API (best |
3599 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2683 | done by writing a wrapper around F<ev.h> that you can include instead and |
3600 | done by writing a wrapper around F<ev.h> that you can include instead and |
2684 | where you can put other configuration options): |
3601 | where you can put other configuration options): |
2685 | |
3602 | |
2686 | #define EV_STANDALONE 1 |
3603 | #define EV_STANDALONE 1 |
2687 | #include "ev.h" |
3604 | #include "ev.h" |
2688 | |
3605 | |
2689 | Both header files and implementation files can be compiled with a C++ |
3606 | Both header files and implementation files can be compiled with a C++ |
2690 | compiler (at least, thats a stated goal, and breakage will be treated |
3607 | compiler (at least, that's a stated goal, and breakage will be treated |
2691 | as a bug). |
3608 | as a bug). |
2692 | |
3609 | |
2693 | You need the following files in your source tree, or in a directory |
3610 | You need the following files in your source tree, or in a directory |
2694 | in your include path (e.g. in libev/ when using -Ilibev): |
3611 | in your include path (e.g. in libev/ when using -Ilibev): |
2695 | |
3612 | |
2696 | ev.h |
3613 | ev.h |
2697 | ev.c |
3614 | ev.c |
2698 | ev_vars.h |
3615 | ev_vars.h |
2699 | ev_wrap.h |
3616 | ev_wrap.h |
2700 | |
3617 | |
2701 | ev_win32.c required on win32 platforms only |
3618 | ev_win32.c required on win32 platforms only |
2702 | |
3619 | |
2703 | ev_select.c only when select backend is enabled (which is enabled by default) |
3620 | ev_select.c only when select backend is enabled (which is enabled by default) |
2704 | ev_poll.c only when poll backend is enabled (disabled by default) |
3621 | ev_poll.c only when poll backend is enabled (disabled by default) |
2705 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
3622 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2706 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
3623 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2707 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
3624 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2708 | |
3625 | |
2709 | F<ev.c> includes the backend files directly when enabled, so you only need |
3626 | F<ev.c> includes the backend files directly when enabled, so you only need |
2710 | to compile this single file. |
3627 | to compile this single file. |
2711 | |
3628 | |
2712 | =head3 LIBEVENT COMPATIBILITY API |
3629 | =head3 LIBEVENT COMPATIBILITY API |
2713 | |
3630 | |
2714 | To include the libevent compatibility API, also include: |
3631 | To include the libevent compatibility API, also include: |
2715 | |
3632 | |
2716 | #include "event.c" |
3633 | #include "event.c" |
2717 | |
3634 | |
2718 | in the file including F<ev.c>, and: |
3635 | in the file including F<ev.c>, and: |
2719 | |
3636 | |
2720 | #include "event.h" |
3637 | #include "event.h" |
2721 | |
3638 | |
2722 | in the files that want to use the libevent API. This also includes F<ev.h>. |
3639 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2723 | |
3640 | |
2724 | You need the following additional files for this: |
3641 | You need the following additional files for this: |
2725 | |
3642 | |
2726 | event.h |
3643 | event.h |
2727 | event.c |
3644 | event.c |
2728 | |
3645 | |
2729 | =head3 AUTOCONF SUPPORT |
3646 | =head3 AUTOCONF SUPPORT |
2730 | |
3647 | |
2731 | Instead of using C<EV_STANDALONE=1> and providing your config in |
3648 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2732 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
3649 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2733 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
3650 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2734 | include F<config.h> and configure itself accordingly. |
3651 | include F<config.h> and configure itself accordingly. |
2735 | |
3652 | |
2736 | For this of course you need the m4 file: |
3653 | For this of course you need the m4 file: |
2737 | |
3654 | |
2738 | libev.m4 |
3655 | libev.m4 |
2739 | |
3656 | |
2740 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3657 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2741 | |
3658 | |
2742 | Libev can be configured via a variety of preprocessor symbols you have to define |
3659 | Libev can be configured via a variety of preprocessor symbols you have to |
2743 | before including any of its files. The default is not to build for multiplicity |
3660 | define before including (or compiling) any of its files. The default in |
2744 | and only include the select backend. |
3661 | the absence of autoconf is documented for every option. |
|
|
3662 | |
|
|
3663 | 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 |
|
|
3665 | to redefine them before including F<ev.h> without breakign compatibility |
|
|
3666 | 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 |
|
|
3668 | settings. |
2745 | |
3669 | |
2746 | =over 4 |
3670 | =over 4 |
2747 | |
3671 | |
2748 | =item EV_STANDALONE |
3672 | =item EV_STANDALONE (h) |
2749 | |
3673 | |
2750 | Must always be C<1> if you do not use autoconf configuration, which |
3674 | Must always be C<1> if you do not use autoconf configuration, which |
2751 | keeps libev from including F<config.h>, and it also defines dummy |
3675 | keeps libev from including F<config.h>, and it also defines dummy |
2752 | implementations for some libevent functions (such as logging, which is not |
3676 | implementations for some libevent functions (such as logging, which is not |
2753 | supported). It will also not define any of the structs usually found in |
3677 | supported). It will also not define any of the structs usually found in |
2754 | F<event.h> that are not directly supported by the libev core alone. |
3678 | F<event.h> that are not directly supported by the libev core alone. |
2755 | |
3679 | |
|
|
3680 | In standalone mode, libev will still try to automatically deduce the |
|
|
3681 | configuration, but has to be more conservative. |
|
|
3682 | |
2756 | =item EV_USE_MONOTONIC |
3683 | =item EV_USE_MONOTONIC |
2757 | |
3684 | |
2758 | If defined to be C<1>, libev will try to detect the availability of the |
3685 | If defined to be C<1>, libev will try to detect the availability of the |
2759 | monotonic clock option at both compiletime and runtime. Otherwise no use |
3686 | monotonic clock option at both compile time and runtime. Otherwise no |
2760 | of the monotonic clock option will be attempted. If you enable this, you |
3687 | use of the monotonic clock option will be attempted. If you enable this, |
2761 | usually have to link against librt or something similar. Enabling it when |
3688 | you usually have to link against librt or something similar. Enabling it |
2762 | the functionality isn't available is safe, though, although you have |
3689 | when the functionality isn't available is safe, though, although you have |
2763 | to make sure you link against any libraries where the C<clock_gettime> |
3690 | to make sure you link against any libraries where the C<clock_gettime> |
2764 | function is hiding in (often F<-lrt>). |
3691 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2765 | |
3692 | |
2766 | =item EV_USE_REALTIME |
3693 | =item EV_USE_REALTIME |
2767 | |
3694 | |
2768 | If defined to be C<1>, libev will try to detect the availability of the |
3695 | If defined to be C<1>, libev will try to detect the availability of the |
2769 | realtime clock option at compiletime (and assume its availability at |
3696 | real-time clock option at compile time (and assume its availability |
2770 | runtime if successful). Otherwise no use of the realtime clock option will |
3697 | at runtime if successful). Otherwise no use of the real-time clock |
2771 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3698 | option will be attempted. This effectively replaces C<gettimeofday> |
2772 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3699 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2773 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3700 | correctness. See the note about libraries in the description of |
|
|
3701 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3702 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3703 | |
|
|
3704 | =item EV_USE_CLOCK_SYSCALL |
|
|
3705 | |
|
|
3706 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3707 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3708 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3709 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3710 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3711 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3712 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3713 | higher, as it simplifies linking (no need for C<-lrt>). |
2774 | |
3714 | |
2775 | =item EV_USE_NANOSLEEP |
3715 | =item EV_USE_NANOSLEEP |
2776 | |
3716 | |
2777 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3717 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2778 | and will use it for delays. Otherwise it will use C<select ()>. |
3718 | and will use it for delays. Otherwise it will use C<select ()>. |
2779 | |
3719 | |
|
|
3720 | =item EV_USE_EVENTFD |
|
|
3721 | |
|
|
3722 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
3723 | 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. |
|
|
3725 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3726 | 2.7 or newer, otherwise disabled. |
|
|
3727 | |
2780 | =item EV_USE_SELECT |
3728 | =item EV_USE_SELECT |
2781 | |
3729 | |
2782 | If undefined or defined to be C<1>, libev will compile in support for the |
3730 | If undefined or defined to be C<1>, libev will compile in support for the |
2783 | C<select>(2) backend. No attempt at autodetection will be done: if no |
3731 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
2784 | other method takes over, select will be it. Otherwise the select backend |
3732 | other method takes over, select will be it. Otherwise the select backend |
2785 | will not be compiled in. |
3733 | will not be compiled in. |
2786 | |
3734 | |
2787 | =item EV_SELECT_USE_FD_SET |
3735 | =item EV_SELECT_USE_FD_SET |
2788 | |
3736 | |
2789 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3737 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2790 | structure. This is useful if libev doesn't compile due to a missing |
3738 | structure. This is useful if libev doesn't compile due to a missing |
2791 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
3739 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2792 | exotic systems. This usually limits the range of file descriptors to some |
3740 | on exotic systems. This usually limits the range of file descriptors to |
2793 | low limit such as 1024 or might have other limitations (winsocket only |
3741 | some low limit such as 1024 or might have other limitations (winsocket |
2794 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3742 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2795 | influence the size of the C<fd_set> used. |
3743 | configures the maximum size of the C<fd_set>. |
2796 | |
3744 | |
2797 | =item EV_SELECT_IS_WINSOCKET |
3745 | =item EV_SELECT_IS_WINSOCKET |
2798 | |
3746 | |
2799 | When defined to C<1>, the select backend will assume that |
3747 | When defined to C<1>, the select backend will assume that |
2800 | select/socket/connect etc. don't understand file descriptors but |
3748 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2802 | be used is the winsock select). This means that it will call |
3750 | be used is the winsock select). This means that it will call |
2803 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3751 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2804 | it is assumed that all these functions actually work on fds, even |
3752 | it is assumed that all these functions actually work on fds, even |
2805 | on win32. Should not be defined on non-win32 platforms. |
3753 | on win32. Should not be defined on non-win32 platforms. |
2806 | |
3754 | |
2807 | =item EV_FD_TO_WIN32_HANDLE |
3755 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2808 | |
3756 | |
2809 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3757 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2810 | file descriptors to socket handles. When not defining this symbol (the |
3758 | file descriptors to socket handles. When not defining this symbol (the |
2811 | default), then libev will call C<_get_osfhandle>, which is usually |
3759 | default), then libev will call C<_get_osfhandle>, which is usually |
2812 | correct. In some cases, programs use their own file descriptor management, |
3760 | correct. In some cases, programs use their own file descriptor management, |
2813 | in which case they can provide this function to map fds to socket handles. |
3761 | in which case they can provide this function to map fds to socket handles. |
2814 | |
3762 | |
|
|
3763 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3764 | |
|
|
3765 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3766 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3767 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3768 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3769 | |
|
|
3770 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3771 | |
|
|
3772 | 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 |
|
|
3774 | file descriptors again. Note that the replacement function has to close |
|
|
3775 | the underlying OS handle. |
|
|
3776 | |
2815 | =item EV_USE_POLL |
3777 | =item EV_USE_POLL |
2816 | |
3778 | |
2817 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3779 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2818 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3780 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2819 | takes precedence over select. |
3781 | takes precedence over select. |
2820 | |
3782 | |
2821 | =item EV_USE_EPOLL |
3783 | =item EV_USE_EPOLL |
2822 | |
3784 | |
2823 | If defined to be C<1>, libev will compile in support for the Linux |
3785 | If defined to be C<1>, libev will compile in support for the Linux |
2824 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3786 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2825 | otherwise another method will be used as fallback. This is the |
3787 | otherwise another method will be used as fallback. This is the preferred |
2826 | preferred backend for GNU/Linux systems. |
3788 | 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. |
2827 | |
3790 | |
2828 | =item EV_USE_KQUEUE |
3791 | =item EV_USE_KQUEUE |
2829 | |
3792 | |
2830 | If defined to be C<1>, libev will compile in support for the BSD style |
3793 | If defined to be C<1>, libev will compile in support for the BSD style |
2831 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
3794 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2844 | otherwise another method will be used as fallback. This is the preferred |
3807 | otherwise another method will be used as fallback. This is the preferred |
2845 | backend for Solaris 10 systems. |
3808 | backend for Solaris 10 systems. |
2846 | |
3809 | |
2847 | =item EV_USE_DEVPOLL |
3810 | =item EV_USE_DEVPOLL |
2848 | |
3811 | |
2849 | reserved for future expansion, works like the USE symbols above. |
3812 | Reserved for future expansion, works like the USE symbols above. |
2850 | |
3813 | |
2851 | =item EV_USE_INOTIFY |
3814 | =item EV_USE_INOTIFY |
2852 | |
3815 | |
2853 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3816 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2854 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3817 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2855 | be detected at runtime. |
3818 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3819 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2856 | |
3820 | |
2857 | =item EV_ATOMIC_T |
3821 | =item EV_ATOMIC_T |
2858 | |
3822 | |
2859 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3823 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2860 | access is atomic with respect to other threads or signal contexts. No such |
3824 | access is atomic with respect to other threads or signal contexts. No such |
2861 | type is easily found in the C language, so you can provide your own type |
3825 | type is easily found in the C language, so you can provide your own type |
2862 | that you know is safe for your purposes. It is used both for signal handler "locking" |
3826 | that you know is safe for your purposes. It is used both for signal handler "locking" |
2863 | as well as for signal and thread safety in C<ev_async> watchers. |
3827 | as well as for signal and thread safety in C<ev_async> watchers. |
2864 | |
3828 | |
2865 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
3829 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2866 | (from F<signal.h>), which is usually good enough on most platforms. |
3830 | (from F<signal.h>), which is usually good enough on most platforms. |
2867 | |
3831 | |
2868 | =item EV_H |
3832 | =item EV_H (h) |
2869 | |
3833 | |
2870 | The name of the F<ev.h> header file used to include it. The default if |
3834 | The name of the F<ev.h> header file used to include it. The default if |
2871 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3835 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2872 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3836 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2873 | |
3837 | |
2874 | =item EV_CONFIG_H |
3838 | =item EV_CONFIG_H (h) |
2875 | |
3839 | |
2876 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3840 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2877 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3841 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2878 | C<EV_H>, above. |
3842 | C<EV_H>, above. |
2879 | |
3843 | |
2880 | =item EV_EVENT_H |
3844 | =item EV_EVENT_H (h) |
2881 | |
3845 | |
2882 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3846 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2883 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3847 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2884 | |
3848 | |
2885 | =item EV_PROTOTYPES |
3849 | =item EV_PROTOTYPES (h) |
2886 | |
3850 | |
2887 | If defined to be C<0>, then F<ev.h> will not define any function |
3851 | If defined to be C<0>, then F<ev.h> will not define any function |
2888 | prototypes, but still define all the structs and other symbols. This is |
3852 | prototypes, but still define all the structs and other symbols. This is |
2889 | occasionally useful if you want to provide your own wrapper functions |
3853 | occasionally useful if you want to provide your own wrapper functions |
2890 | around libev functions. |
3854 | around libev functions. |
… | |
… | |
2909 | When doing priority-based operations, libev usually has to linearly search |
3873 | When doing priority-based operations, libev usually has to linearly search |
2910 | all the priorities, so having many of them (hundreds) uses a lot of space |
3874 | all the priorities, so having many of them (hundreds) uses a lot of space |
2911 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3875 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2912 | fine. |
3876 | fine. |
2913 | |
3877 | |
2914 | If your embedding app does not need any priorities, defining these both to |
3878 | If your embedding application does not need any priorities, defining these |
2915 | C<0> will save some memory and cpu. |
3879 | both to C<0> will save some memory and CPU. |
2916 | |
3880 | |
2917 | =item EV_PERIODIC_ENABLE |
3881 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3882 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3883 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
2918 | |
3884 | |
2919 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3885 | If undefined or defined to be C<1> (and the platform supports it), then |
2920 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3886 | the respective watcher type is supported. If defined to be C<0>, then it |
2921 | code. |
3887 | is not. Disabling watcher types mainly saves codesize. |
2922 | |
3888 | |
2923 | =item EV_IDLE_ENABLE |
3889 | =item EV_FEATURES |
2924 | |
|
|
2925 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
2926 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
2927 | code. |
|
|
2928 | |
|
|
2929 | =item EV_EMBED_ENABLE |
|
|
2930 | |
|
|
2931 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
2932 | defined to be C<0>, then they are not. |
|
|
2933 | |
|
|
2934 | =item EV_STAT_ENABLE |
|
|
2935 | |
|
|
2936 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
2937 | defined to be C<0>, then they are not. |
|
|
2938 | |
|
|
2939 | =item EV_FORK_ENABLE |
|
|
2940 | |
|
|
2941 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2942 | defined to be C<0>, then they are not. |
|
|
2943 | |
|
|
2944 | =item EV_ASYNC_ENABLE |
|
|
2945 | |
|
|
2946 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
2947 | defined to be C<0>, then they are not. |
|
|
2948 | |
|
|
2949 | =item EV_MINIMAL |
|
|
2950 | |
3890 | |
2951 | If you need to shave off some kilobytes of code at the expense of some |
3891 | If you need to shave off some kilobytes of code at the expense of some |
2952 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3892 | speed (but with the full API), you can define this symbol to request |
2953 | some inlining decisions, saves roughly 30% codesize of amd64. |
3893 | certain subsets of functionality. The default is to enable all features |
|
|
3894 | 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 | |
|
|
3899 | 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 |
|
|
3901 | additional parts you want, for example if you want everything minimal, |
|
|
3902 | but multiple event loop support, async and child watchers and the poll |
|
|
3903 | backend, use this: |
|
|
3904 | |
|
|
3905 | #define EV_FEATURES 0 |
|
|
3906 | #define EV_MULTIPLICITY 1 |
|
|
3907 | #define EV_USE_POLL 1 |
|
|
3908 | #define EV_CHILD_ENABLE 1 |
|
|
3909 | #define EV_ASYNC_ENABLE 1 |
|
|
3910 | |
|
|
3911 | The actual value is a bitset, it can be a combination of the following |
|
|
3912 | values: |
|
|
3913 | |
|
|
3914 | =over 4 |
|
|
3915 | |
|
|
3916 | =item C<1> - faster/larger code |
|
|
3917 | |
|
|
3918 | Use larger code to speed up some operations. |
|
|
3919 | |
|
|
3920 | Currently this is used to override some inlining decisions (enlarging the roughly |
|
|
3921 | 30% code size on amd64. |
|
|
3922 | |
|
|
3923 | Also disables C<assert>'s in the code, unless you define C<NDEBUG> |
|
|
3924 | explicitly to C<0>. |
|
|
3925 | |
|
|
3926 | Use of compiler flags such as C<-Os> with gcc that optimise for size are |
|
|
3927 | recommended when disabling this feature. |
|
|
3928 | |
|
|
3929 | =item C<2> - faster/larger data structures |
|
|
3930 | |
|
|
3931 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3932 | hash table sizes and so on. This will usually further increase codesize |
|
|
3933 | and can additionally have an effect on the size of data structures at |
|
|
3934 | runtime. |
|
|
3935 | |
|
|
3936 | =item C<4> - full API configuration |
|
|
3937 | |
|
|
3938 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3939 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3940 | |
|
|
3941 | It also enables a lot of the "lesser used" core API functions. See C<ev.h> |
|
|
3942 | for details on which parts of the API are still available without this |
|
|
3943 | feature, and do not complain if this subset changes over time. |
|
|
3944 | |
|
|
3945 | =item C<8> - enable all optional watcher types |
|
|
3946 | |
|
|
3947 | Enables all optional watcher types. If you want to selectively enable |
|
|
3948 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3949 | embed, async, child...) you can enable them manually by defining |
|
|
3950 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3951 | |
|
|
3952 | =item C<16> - enable all backends |
|
|
3953 | |
|
|
3954 | This enables all backends - without this feature, you need to enable at |
|
|
3955 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3956 | |
|
|
3957 | =item C<32> - enable OS-specific "helper" APIs |
|
|
3958 | |
|
|
3959 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3960 | default. |
|
|
3961 | |
|
|
3962 | =back |
|
|
3963 | |
|
|
3964 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3965 | reduces the compiled size of libev from 24.7Kb to 6.5Kb on my GNU/Linux |
|
|
3966 | amd64 system, while still giving you I/O watchers, timers and monotonic |
|
|
3967 | clock support. |
|
|
3968 | |
|
|
3969 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3970 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3971 | your program might be left out as well - a binary starting a timer and an |
|
|
3972 | I/O watcher then might come out at only 5Kb. |
|
|
3973 | |
|
|
3974 | =item EV_AVOID_STDIO |
|
|
3975 | |
|
|
3976 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3977 | functions (printf, scanf, perror etc.). This will increase the codesize |
|
|
3978 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3979 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3980 | big. |
|
|
3981 | |
|
|
3982 | Note that error messages might become less precise when this option is |
|
|
3983 | enabled. |
|
|
3984 | |
|
|
3985 | =item EV_NSIG |
|
|
3986 | |
|
|
3987 | The highest supported signal number, +1 (or, the number of |
|
|
3988 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3989 | automatically, but sometimes this fails, in which case it can be |
|
|
3990 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3991 | good for about any system in existance) can save some memory, as libev |
|
|
3992 | statically allocates some 12-24 bytes per signal number. |
2954 | |
3993 | |
2955 | =item EV_PID_HASHSIZE |
3994 | =item EV_PID_HASHSIZE |
2956 | |
3995 | |
2957 | C<ev_child> watchers use a small hash table to distribute workload by |
3996 | C<ev_child> watchers use a small hash table to distribute workload by |
2958 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3997 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
2959 | than enough. If you need to manage thousands of children you might want to |
3998 | usually more than enough. If you need to manage thousands of children you |
2960 | increase this value (I<must> be a power of two). |
3999 | might want to increase this value (I<must> be a power of two). |
2961 | |
4000 | |
2962 | =item EV_INOTIFY_HASHSIZE |
4001 | =item EV_INOTIFY_HASHSIZE |
2963 | |
4002 | |
2964 | C<ev_stat> watchers use a small hash table to distribute workload by |
4003 | C<ev_stat> watchers use a small hash table to distribute workload by |
2965 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4004 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
2966 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4005 | disabled), usually more than enough. If you need to manage thousands of |
2967 | watchers you might want to increase this value (I<must> be a power of |
4006 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
2968 | two). |
4007 | power of two). |
|
|
4008 | |
|
|
4009 | =item EV_USE_4HEAP |
|
|
4010 | |
|
|
4011 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4012 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
4013 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
4014 | faster performance with many (thousands) of watchers. |
|
|
4015 | |
|
|
4016 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4017 | will be C<0>. |
|
|
4018 | |
|
|
4019 | =item EV_HEAP_CACHE_AT |
|
|
4020 | |
|
|
4021 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4022 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
4023 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
4024 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
4025 | but avoids random read accesses on heap changes. This improves performance |
|
|
4026 | noticeably with many (hundreds) of watchers. |
|
|
4027 | |
|
|
4028 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4029 | will be C<0>. |
|
|
4030 | |
|
|
4031 | =item EV_VERIFY |
|
|
4032 | |
|
|
4033 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
4034 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
4035 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
4036 | called. If set to C<2>, then the internal verification code will be |
|
|
4037 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
4038 | verification code will be called very frequently, which will slow down |
|
|
4039 | libev considerably. |
|
|
4040 | |
|
|
4041 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4042 | will be C<0>. |
2969 | |
4043 | |
2970 | =item EV_COMMON |
4044 | =item EV_COMMON |
2971 | |
4045 | |
2972 | By default, all watchers have a C<void *data> member. By redefining |
4046 | By default, all watchers have a C<void *data> member. By redefining |
2973 | this macro to a something else you can include more and other types of |
4047 | this macro to a something else you can include more and other types of |
2974 | members. You have to define it each time you include one of the files, |
4048 | members. You have to define it each time you include one of the files, |
2975 | though, and it must be identical each time. |
4049 | though, and it must be identical each time. |
2976 | |
4050 | |
2977 | For example, the perl EV module uses something like this: |
4051 | For example, the perl EV module uses something like this: |
2978 | |
4052 | |
2979 | #define EV_COMMON \ |
4053 | #define EV_COMMON \ |
2980 | SV *self; /* contains this struct */ \ |
4054 | SV *self; /* contains this struct */ \ |
2981 | SV *cb_sv, *fh /* note no trailing ";" */ |
4055 | SV *cb_sv, *fh /* note no trailing ";" */ |
2982 | |
4056 | |
2983 | =item EV_CB_DECLARE (type) |
4057 | =item EV_CB_DECLARE (type) |
2984 | |
4058 | |
2985 | =item EV_CB_INVOKE (watcher, revents) |
4059 | =item EV_CB_INVOKE (watcher, revents) |
2986 | |
4060 | |
… | |
… | |
2991 | definition and a statement, respectively. See the F<ev.h> header file for |
4065 | definition and a statement, respectively. See the F<ev.h> header file for |
2992 | their default definitions. One possible use for overriding these is to |
4066 | their default definitions. One possible use for overriding these is to |
2993 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4067 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2994 | method calls instead of plain function calls in C++. |
4068 | method calls instead of plain function calls in C++. |
2995 | |
4069 | |
|
|
4070 | =back |
|
|
4071 | |
2996 | =head2 EXPORTED API SYMBOLS |
4072 | =head2 EXPORTED API SYMBOLS |
2997 | |
4073 | |
2998 | If you need to re-export the API (e.g. via a dll) and you need a list of |
4074 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
2999 | exported symbols, you can use the provided F<Symbol.*> files which list |
4075 | exported symbols, you can use the provided F<Symbol.*> files which list |
3000 | all public symbols, one per line: |
4076 | all public symbols, one per line: |
3001 | |
4077 | |
3002 | Symbols.ev for libev proper |
4078 | Symbols.ev for libev proper |
3003 | Symbols.event for the libevent emulation |
4079 | Symbols.event for the libevent emulation |
3004 | |
4080 | |
3005 | This can also be used to rename all public symbols to avoid clashes with |
4081 | This can also be used to rename all public symbols to avoid clashes with |
3006 | multiple versions of libev linked together (which is obviously bad in |
4082 | multiple versions of libev linked together (which is obviously bad in |
3007 | itself, but sometimes it is inconvinient to avoid this). |
4083 | itself, but sometimes it is inconvenient to avoid this). |
3008 | |
4084 | |
3009 | A sed command like this will create wrapper C<#define>'s that you need to |
4085 | A sed command like this will create wrapper C<#define>'s that you need to |
3010 | include before including F<ev.h>: |
4086 | include before including F<ev.h>: |
3011 | |
4087 | |
3012 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
4088 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
… | |
… | |
3029 | file. |
4105 | file. |
3030 | |
4106 | |
3031 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4107 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3032 | that everybody includes and which overrides some configure choices: |
4108 | that everybody includes and which overrides some configure choices: |
3033 | |
4109 | |
3034 | #define EV_MINIMAL 1 |
4110 | #define EV_FEATURES 0 |
3035 | #define EV_USE_POLL 0 |
4111 | #define EV_USE_SELECT 1 |
3036 | #define EV_MULTIPLICITY 0 |
|
|
3037 | #define EV_PERIODIC_ENABLE 0 |
|
|
3038 | #define EV_STAT_ENABLE 0 |
|
|
3039 | #define EV_FORK_ENABLE 0 |
|
|
3040 | #define EV_CONFIG_H <config.h> |
4112 | #define EV_CONFIG_H <config.h> |
3041 | #define EV_MINPRI 0 |
|
|
3042 | #define EV_MAXPRI 0 |
|
|
3043 | |
4113 | |
3044 | #include "ev++.h" |
4114 | #include "ev++.h" |
3045 | |
4115 | |
3046 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4116 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3047 | |
4117 | |
3048 | #include "ev_cpp.h" |
4118 | #include "ev_cpp.h" |
3049 | #include "ev.c" |
4119 | #include "ev.c" |
3050 | |
4120 | |
|
|
4121 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3051 | |
4122 | |
3052 | =head1 COMPLEXITIES |
4123 | =head2 THREADS AND COROUTINES |
3053 | |
4124 | |
3054 | In this section the complexities of (many of) the algorithms used inside |
4125 | =head3 THREADS |
3055 | libev will be explained. For complexity discussions about backends see the |
|
|
3056 | documentation for C<ev_default_init>. |
|
|
3057 | |
4126 | |
3058 | All of the following are about amortised time: If an array needs to be |
4127 | All libev functions are reentrant and thread-safe unless explicitly |
3059 | extended, libev needs to realloc and move the whole array, but this |
4128 | documented otherwise, but libev implements no locking itself. This means |
3060 | happens asymptotically never with higher number of elements, so O(1) might |
4129 | that you can use as many loops as you want in parallel, as long as there |
3061 | mean it might do a lengthy realloc operation in rare cases, but on average |
4130 | are no concurrent calls into any libev function with the same loop |
3062 | it is much faster and asymptotically approaches constant time. |
4131 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4132 | of course): libev guarantees that different event loops share no data |
|
|
4133 | structures that need any locking. |
|
|
4134 | |
|
|
4135 | Or to put it differently: calls with different loop parameters can be done |
|
|
4136 | concurrently from multiple threads, calls with the same loop parameter |
|
|
4137 | must be done serially (but can be done from different threads, as long as |
|
|
4138 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
4139 | a mutex per loop). |
|
|
4140 | |
|
|
4141 | Specifically to support threads (and signal handlers), libev implements |
|
|
4142 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4143 | concurrency on the same event loop, namely waking it up "from the |
|
|
4144 | outside". |
|
|
4145 | |
|
|
4146 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4147 | without or something else still) is best for your problem, then I cannot |
|
|
4148 | help you, but here is some generic advice: |
3063 | |
4149 | |
3064 | =over 4 |
4150 | =over 4 |
3065 | |
4151 | |
3066 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4152 | =item * most applications have a main thread: use the default libev loop |
|
|
4153 | in that thread, or create a separate thread running only the default loop. |
3067 | |
4154 | |
3068 | This means that, when you have a watcher that triggers in one hour and |
4155 | This helps integrating other libraries or software modules that use libev |
3069 | there are 100 watchers that would trigger before that then inserting will |
4156 | themselves and don't care/know about threading. |
3070 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3071 | |
4157 | |
3072 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4158 | =item * one loop per thread is usually a good model. |
3073 | |
4159 | |
3074 | That means that changing a timer costs less than removing/adding them |
4160 | Doing this is almost never wrong, sometimes a better-performance model |
3075 | as only the relative motion in the event queue has to be paid for. |
4161 | exists, but it is always a good start. |
3076 | |
4162 | |
3077 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4163 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
4164 | loop is handed through multiple threads in a kind of round-robin fashion. |
3078 | |
4165 | |
3079 | These just add the watcher into an array or at the head of a list. |
4166 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
4167 | better than you currently do :-) |
3080 | |
4168 | |
3081 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4169 | =item * often you need to talk to some other thread which blocks in the |
|
|
4170 | event loop. |
3082 | |
4171 | |
3083 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4172 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
4173 | (or from signal contexts...). |
3084 | |
4174 | |
3085 | These watchers are stored in lists then need to be walked to find the |
4175 | An example use would be to communicate signals or other events that only |
3086 | correct watcher to remove. The lists are usually short (you don't usually |
4176 | work in the default loop by registering the signal watcher with the |
3087 | have many watchers waiting for the same fd or signal). |
4177 | default loop and triggering an C<ev_async> watcher from the default loop |
3088 | |
4178 | watcher callback into the event loop interested in the signal. |
3089 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3090 | |
|
|
3091 | By virtue of using a binary heap, the next timer is always found at the |
|
|
3092 | beginning of the storage array. |
|
|
3093 | |
|
|
3094 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3095 | |
|
|
3096 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3097 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3098 | on backend and wether C<ev_io_set> was used). |
|
|
3099 | |
|
|
3100 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3101 | |
|
|
3102 | =item Priority handling: O(number_of_priorities) |
|
|
3103 | |
|
|
3104 | Priorities are implemented by allocating some space for each |
|
|
3105 | priority. When doing priority-based operations, libev usually has to |
|
|
3106 | linearly search all the priorities, but starting/stopping and activating |
|
|
3107 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3108 | |
|
|
3109 | =item Sending an ev_async: O(1) |
|
|
3110 | |
|
|
3111 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3112 | |
|
|
3113 | =item Processing signals: O(max_signal_number) |
|
|
3114 | |
|
|
3115 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3116 | calls in the current loop iteration. Checking for async and signal events |
|
|
3117 | involves iterating over all running async watchers or all signal numbers. |
|
|
3118 | |
4179 | |
3119 | =back |
4180 | =back |
3120 | |
4181 | |
|
|
4182 | =head4 THREAD LOCKING EXAMPLE |
3121 | |
4183 | |
3122 | =head1 Win32 platform limitations and workarounds |
4184 | Here is a fictitious example of how to run an event loop in a different |
|
|
4185 | thread than where callbacks are being invoked and watchers are |
|
|
4186 | created/added/removed. |
|
|
4187 | |
|
|
4188 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4189 | which uses exactly this technique (which is suited for many high-level |
|
|
4190 | languages). |
|
|
4191 | |
|
|
4192 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4193 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4194 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4195 | |
|
|
4196 | First, you need to associate some data with the event loop: |
|
|
4197 | |
|
|
4198 | typedef struct { |
|
|
4199 | mutex_t lock; /* global loop lock */ |
|
|
4200 | ev_async async_w; |
|
|
4201 | thread_t tid; |
|
|
4202 | cond_t invoke_cv; |
|
|
4203 | } userdata; |
|
|
4204 | |
|
|
4205 | void prepare_loop (EV_P) |
|
|
4206 | { |
|
|
4207 | // for simplicity, we use a static userdata struct. |
|
|
4208 | static userdata u; |
|
|
4209 | |
|
|
4210 | ev_async_init (&u->async_w, async_cb); |
|
|
4211 | ev_async_start (EV_A_ &u->async_w); |
|
|
4212 | |
|
|
4213 | pthread_mutex_init (&u->lock, 0); |
|
|
4214 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4215 | |
|
|
4216 | // now associate this with the loop |
|
|
4217 | ev_set_userdata (EV_A_ u); |
|
|
4218 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4219 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4220 | |
|
|
4221 | // then create the thread running ev_loop |
|
|
4222 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4223 | } |
|
|
4224 | |
|
|
4225 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4226 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4227 | that might have been added: |
|
|
4228 | |
|
|
4229 | static void |
|
|
4230 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4231 | { |
|
|
4232 | // just used for the side effects |
|
|
4233 | } |
|
|
4234 | |
|
|
4235 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4236 | protecting the loop data, respectively. |
|
|
4237 | |
|
|
4238 | static void |
|
|
4239 | l_release (EV_P) |
|
|
4240 | { |
|
|
4241 | userdata *u = ev_userdata (EV_A); |
|
|
4242 | pthread_mutex_unlock (&u->lock); |
|
|
4243 | } |
|
|
4244 | |
|
|
4245 | static void |
|
|
4246 | l_acquire (EV_P) |
|
|
4247 | { |
|
|
4248 | userdata *u = ev_userdata (EV_A); |
|
|
4249 | pthread_mutex_lock (&u->lock); |
|
|
4250 | } |
|
|
4251 | |
|
|
4252 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4253 | into C<ev_loop>: |
|
|
4254 | |
|
|
4255 | void * |
|
|
4256 | l_run (void *thr_arg) |
|
|
4257 | { |
|
|
4258 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4259 | |
|
|
4260 | l_acquire (EV_A); |
|
|
4261 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4262 | ev_loop (EV_A_ 0); |
|
|
4263 | l_release (EV_A); |
|
|
4264 | |
|
|
4265 | return 0; |
|
|
4266 | } |
|
|
4267 | |
|
|
4268 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4269 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4270 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4271 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4272 | and b) skipping inter-thread-communication when there are no pending |
|
|
4273 | watchers is very beneficial): |
|
|
4274 | |
|
|
4275 | static void |
|
|
4276 | l_invoke (EV_P) |
|
|
4277 | { |
|
|
4278 | userdata *u = ev_userdata (EV_A); |
|
|
4279 | |
|
|
4280 | while (ev_pending_count (EV_A)) |
|
|
4281 | { |
|
|
4282 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4283 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4284 | } |
|
|
4285 | } |
|
|
4286 | |
|
|
4287 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4288 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4289 | thread to continue: |
|
|
4290 | |
|
|
4291 | static void |
|
|
4292 | real_invoke_pending (EV_P) |
|
|
4293 | { |
|
|
4294 | userdata *u = ev_userdata (EV_A); |
|
|
4295 | |
|
|
4296 | pthread_mutex_lock (&u->lock); |
|
|
4297 | ev_invoke_pending (EV_A); |
|
|
4298 | pthread_cond_signal (&u->invoke_cv); |
|
|
4299 | pthread_mutex_unlock (&u->lock); |
|
|
4300 | } |
|
|
4301 | |
|
|
4302 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4303 | event loop, you will now have to lock: |
|
|
4304 | |
|
|
4305 | ev_timer timeout_watcher; |
|
|
4306 | userdata *u = ev_userdata (EV_A); |
|
|
4307 | |
|
|
4308 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4309 | |
|
|
4310 | pthread_mutex_lock (&u->lock); |
|
|
4311 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4312 | ev_async_send (EV_A_ &u->async_w); |
|
|
4313 | pthread_mutex_unlock (&u->lock); |
|
|
4314 | |
|
|
4315 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4316 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4317 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4318 | watchers in the next event loop iteration. |
|
|
4319 | |
|
|
4320 | =head3 COROUTINES |
|
|
4321 | |
|
|
4322 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
4323 | libev fully supports nesting calls to its functions from different |
|
|
4324 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
4325 | different coroutines, and switch freely between both coroutines running |
|
|
4326 | the loop, as long as you don't confuse yourself). The only exception is |
|
|
4327 | that you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
4328 | |
|
|
4329 | Care has been taken to ensure that libev does not keep local state inside |
|
|
4330 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
4331 | they do not call any callbacks. |
|
|
4332 | |
|
|
4333 | =head2 COMPILER WARNINGS |
|
|
4334 | |
|
|
4335 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4336 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4337 | scared by this. |
|
|
4338 | |
|
|
4339 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
4340 | has different warnings, and each user has different tastes regarding |
|
|
4341 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4342 | targeting a specific compiler and compiler-version. |
|
|
4343 | |
|
|
4344 | Another reason is that some compiler warnings require elaborate |
|
|
4345 | workarounds, or other changes to the code that make it less clear and less |
|
|
4346 | maintainable. |
|
|
4347 | |
|
|
4348 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4349 | wrong (because they don't actually warn about the condition their message |
|
|
4350 | seems to warn about). For example, certain older gcc versions had some |
|
|
4351 | warnings that resulted an extreme number of false positives. These have |
|
|
4352 | been fixed, but some people still insist on making code warn-free with |
|
|
4353 | such buggy versions. |
|
|
4354 | |
|
|
4355 | While libev is written to generate as few warnings as possible, |
|
|
4356 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4357 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4358 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4359 | warnings, not errors, or proof of bugs. |
|
|
4360 | |
|
|
4361 | |
|
|
4362 | =head2 VALGRIND |
|
|
4363 | |
|
|
4364 | Valgrind has a special section here because it is a popular tool that is |
|
|
4365 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
4366 | |
|
|
4367 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4368 | in libev, then check twice: If valgrind reports something like: |
|
|
4369 | |
|
|
4370 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4371 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4372 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
4373 | |
|
|
4374 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4375 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
4376 | |
|
|
4377 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4378 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4379 | although an acceptable workaround has been found here), or it might be |
|
|
4380 | confused. |
|
|
4381 | |
|
|
4382 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
4383 | make it into some kind of religion. |
|
|
4384 | |
|
|
4385 | If you are unsure about something, feel free to contact the mailing list |
|
|
4386 | with the full valgrind report and an explanation on why you think this |
|
|
4387 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4388 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4389 | of learning how to interpret valgrind properly. |
|
|
4390 | |
|
|
4391 | If you need, for some reason, empty reports from valgrind for your project |
|
|
4392 | I suggest using suppression lists. |
|
|
4393 | |
|
|
4394 | |
|
|
4395 | =head1 PORTABILITY NOTES |
|
|
4396 | |
|
|
4397 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3123 | |
4398 | |
3124 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4399 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3125 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4400 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3126 | model. Libev still offers limited functionality on this platform in |
4401 | model. Libev still offers limited functionality on this platform in |
3127 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4402 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3128 | descriptors. This only applies when using Win32 natively, not when using |
4403 | descriptors. This only applies when using Win32 natively, not when using |
3129 | e.g. cygwin. |
4404 | e.g. cygwin. |
3130 | |
4405 | |
|
|
4406 | Lifting these limitations would basically require the full |
|
|
4407 | re-implementation of the I/O system. If you are into these kinds of |
|
|
4408 | things, then note that glib does exactly that for you in a very portable |
|
|
4409 | way (note also that glib is the slowest event library known to man). |
|
|
4410 | |
3131 | There is no supported compilation method available on windows except |
4411 | There is no supported compilation method available on windows except |
3132 | embedding it into other applications. |
4412 | embedding it into other applications. |
3133 | |
4413 | |
|
|
4414 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4415 | tries its best, but under most conditions, signals will simply not work. |
|
|
4416 | |
|
|
4417 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
4418 | accept large writes: instead of resulting in a partial write, windows will |
|
|
4419 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
4420 | so make sure you only write small amounts into your sockets (less than a |
|
|
4421 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
4422 | available). |
|
|
4423 | |
3134 | Due to the many, low, and arbitrary limits on the win32 platform and the |
4424 | Due to the many, low, and arbitrary limits on the win32 platform and |
3135 | abysmal performance of winsockets, using a large number of sockets is not |
4425 | the abysmal performance of winsockets, using a large number of sockets |
3136 | recommended (and not reasonable). If your program needs to use more than |
4426 | is not recommended (and not reasonable). If your program needs to use |
3137 | a hundred or so sockets, then likely it needs to use a totally different |
4427 | more than a hundred or so sockets, then likely it needs to use a totally |
3138 | implementation for windows, as libev offers the POSIX model, which cannot |
4428 | different implementation for windows, as libev offers the POSIX readiness |
3139 | be implemented efficiently on windows (microsoft monopoly games). |
4429 | notification model, which cannot be implemented efficiently on windows |
|
|
4430 | (due to Microsoft monopoly games). |
|
|
4431 | |
|
|
4432 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
4433 | section for details) and use the following F<evwrap.h> header file instead |
|
|
4434 | of F<ev.h>: |
|
|
4435 | |
|
|
4436 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
4437 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
4438 | |
|
|
4439 | #include "ev.h" |
|
|
4440 | |
|
|
4441 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
4442 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
4443 | |
|
|
4444 | #include "evwrap.h" |
|
|
4445 | #include "ev.c" |
3140 | |
4446 | |
3141 | =over 4 |
4447 | =over 4 |
3142 | |
4448 | |
3143 | =item The winsocket select function |
4449 | =item The winsocket select function |
3144 | |
4450 | |
3145 | The winsocket C<select> function doesn't follow POSIX in that it requires |
4451 | The winsocket C<select> function doesn't follow POSIX in that it |
3146 | socket I<handles> and not socket I<file descriptors>. This makes select |
4452 | requires socket I<handles> and not socket I<file descriptors> (it is |
3147 | very inefficient, and also requires a mapping from file descriptors |
4453 | also extremely buggy). This makes select very inefficient, and also |
3148 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
4454 | requires a mapping from file descriptors to socket handles (the Microsoft |
3149 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
4455 | C runtime provides the function C<_open_osfhandle> for this). See the |
3150 | symbols for more info. |
4456 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
4457 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
3151 | |
4458 | |
3152 | The configuration for a "naked" win32 using the microsoft runtime |
4459 | The configuration for a "naked" win32 using the Microsoft runtime |
3153 | libraries and raw winsocket select is: |
4460 | libraries and raw winsocket select is: |
3154 | |
4461 | |
3155 | #define EV_USE_SELECT 1 |
4462 | #define EV_USE_SELECT 1 |
3156 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4463 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3157 | |
4464 | |
3158 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4465 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3159 | complexity in the O(n²) range when using win32. |
4466 | complexity in the O(n²) range when using win32. |
3160 | |
4467 | |
3161 | =item Limited number of file descriptors |
4468 | =item Limited number of file descriptors |
3162 | |
4469 | |
3163 | Windows has numerous arbitrary (and low) limits on things. Early versions |
4470 | Windows has numerous arbitrary (and low) limits on things. |
3164 | of winsocket's select only supported waiting for a max. of C<64> handles |
4471 | |
|
|
4472 | Early versions of winsocket's select only supported waiting for a maximum |
3165 | (probably owning to the fact that all windows kernels can only wait for |
4473 | of C<64> handles (probably owning to the fact that all windows kernels |
3166 | C<64> things at the same time internally; microsoft recommends spawning a |
4474 | can only wait for C<64> things at the same time internally; Microsoft |
3167 | chain of threads and wait for 63 handles and the previous thread in each). |
4475 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4476 | previous thread in each. Sounds great!). |
3168 | |
4477 | |
3169 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4478 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3170 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4479 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3171 | call (which might be in libev or elsewhere, for example, perl does its own |
4480 | call (which might be in libev or elsewhere, for example, perl and many |
3172 | select emulation on windows). |
4481 | other interpreters do their own select emulation on windows). |
3173 | |
4482 | |
3174 | Another limit is the number of file descriptors in the microsoft runtime |
4483 | Another limit is the number of file descriptors in the Microsoft runtime |
3175 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4484 | libraries, which by default is C<64> (there must be a hidden I<64> |
3176 | or something like this inside microsoft). You can increase this by calling |
4485 | fetish or something like this inside Microsoft). You can increase this |
3177 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4486 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3178 | arbitrary limit), but is broken in many versions of the microsoft runtime |
4487 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3179 | libraries. |
|
|
3180 | |
|
|
3181 | This might get you to about C<512> or C<2048> sockets (depending on |
4488 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3182 | windows version and/or the phase of the moon). To get more, you need to |
4489 | (depending on windows version and/or the phase of the moon). To get more, |
3183 | wrap all I/O functions and provide your own fd management, but the cost of |
4490 | you need to wrap all I/O functions and provide your own fd management, but |
3184 | calling select (O(n²)) will likely make this unworkable. |
4491 | the cost of calling select (O(n²)) will likely make this unworkable. |
3185 | |
4492 | |
3186 | =back |
4493 | =back |
3187 | |
4494 | |
|
|
4495 | =head2 PORTABILITY REQUIREMENTS |
|
|
4496 | |
|
|
4497 | In addition to a working ISO-C implementation and of course the |
|
|
4498 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4499 | |
|
|
4500 | =over 4 |
|
|
4501 | |
|
|
4502 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
4503 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
4504 | |
|
|
4505 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4506 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
4507 | assumes that the same (machine) code can be used to call any watcher |
|
|
4508 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4509 | calls them using an C<ev_watcher *> internally. |
|
|
4510 | |
|
|
4511 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
4512 | |
|
|
4513 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
4514 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
4515 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
4516 | believed to be sufficiently portable. |
|
|
4517 | |
|
|
4518 | =item C<sigprocmask> must work in a threaded environment |
|
|
4519 | |
|
|
4520 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
4521 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
4522 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
4523 | thread" or will block signals process-wide, both behaviours would |
|
|
4524 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
4525 | C<pthread_sigmask> could complicate things, however. |
|
|
4526 | |
|
|
4527 | The most portable way to handle signals is to block signals in all threads |
|
|
4528 | except the initial one, and run the default loop in the initial thread as |
|
|
4529 | well. |
|
|
4530 | |
|
|
4531 | =item C<long> must be large enough for common memory allocation sizes |
|
|
4532 | |
|
|
4533 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
4534 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
4535 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4536 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
4537 | watchers. |
|
|
4538 | |
|
|
4539 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
4540 | |
|
|
4541 | The type C<double> is used to represent timestamps. It is required to |
|
|
4542 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4543 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4544 | implementations implementing IEEE 754, which is basically all existing |
|
|
4545 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4546 | 2200. |
|
|
4547 | |
|
|
4548 | =back |
|
|
4549 | |
|
|
4550 | If you know of other additional requirements drop me a note. |
|
|
4551 | |
|
|
4552 | |
|
|
4553 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
4554 | |
|
|
4555 | In this section the complexities of (many of) the algorithms used inside |
|
|
4556 | libev will be documented. For complexity discussions about backends see |
|
|
4557 | the documentation for C<ev_default_init>. |
|
|
4558 | |
|
|
4559 | All of the following are about amortised time: If an array needs to be |
|
|
4560 | extended, libev needs to realloc and move the whole array, but this |
|
|
4561 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
4562 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4563 | average it is much faster and asymptotically approaches constant time. |
|
|
4564 | |
|
|
4565 | =over 4 |
|
|
4566 | |
|
|
4567 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
4568 | |
|
|
4569 | This means that, when you have a watcher that triggers in one hour and |
|
|
4570 | there are 100 watchers that would trigger before that, then inserting will |
|
|
4571 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
4572 | |
|
|
4573 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
4574 | |
|
|
4575 | That means that changing a timer costs less than removing/adding them, |
|
|
4576 | as only the relative motion in the event queue has to be paid for. |
|
|
4577 | |
|
|
4578 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
4579 | |
|
|
4580 | These just add the watcher into an array or at the head of a list. |
|
|
4581 | |
|
|
4582 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
4583 | |
|
|
4584 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
4585 | |
|
|
4586 | These watchers are stored in lists, so they need to be walked to find the |
|
|
4587 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
4588 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4589 | is rare). |
|
|
4590 | |
|
|
4591 | =item Finding the next timer in each loop iteration: O(1) |
|
|
4592 | |
|
|
4593 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4594 | fixed position in the storage array. |
|
|
4595 | |
|
|
4596 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4597 | |
|
|
4598 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4599 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4600 | on backend and whether C<ev_io_set> was used). |
|
|
4601 | |
|
|
4602 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4603 | |
|
|
4604 | =item Priority handling: O(number_of_priorities) |
|
|
4605 | |
|
|
4606 | Priorities are implemented by allocating some space for each |
|
|
4607 | priority. When doing priority-based operations, libev usually has to |
|
|
4608 | linearly search all the priorities, but starting/stopping and activating |
|
|
4609 | watchers becomes O(1) with respect to priority handling. |
|
|
4610 | |
|
|
4611 | =item Sending an ev_async: O(1) |
|
|
4612 | |
|
|
4613 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4614 | |
|
|
4615 | =item Processing signals: O(max_signal_number) |
|
|
4616 | |
|
|
4617 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4618 | calls in the current loop iteration. Checking for async and signal events |
|
|
4619 | involves iterating over all running async watchers or all signal numbers. |
|
|
4620 | |
|
|
4621 | =back |
|
|
4622 | |
|
|
4623 | |
|
|
4624 | =head1 GLOSSARY |
|
|
4625 | |
|
|
4626 | =over 4 |
|
|
4627 | |
|
|
4628 | =item active |
|
|
4629 | |
|
|
4630 | A watcher is active as long as it has been started (has been attached to |
|
|
4631 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4632 | |
|
|
4633 | =item application |
|
|
4634 | |
|
|
4635 | In this document, an application is whatever is using libev. |
|
|
4636 | |
|
|
4637 | =item callback |
|
|
4638 | |
|
|
4639 | The address of a function that is called when some event has been |
|
|
4640 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4641 | received the event, and the actual event bitset. |
|
|
4642 | |
|
|
4643 | =item callback invocation |
|
|
4644 | |
|
|
4645 | The act of calling the callback associated with a watcher. |
|
|
4646 | |
|
|
4647 | =item event |
|
|
4648 | |
|
|
4649 | A change of state of some external event, such as data now being available |
|
|
4650 | for reading on a file descriptor, time having passed or simply not having |
|
|
4651 | any other events happening anymore. |
|
|
4652 | |
|
|
4653 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4654 | C<EV_TIMEOUT>). |
|
|
4655 | |
|
|
4656 | =item event library |
|
|
4657 | |
|
|
4658 | A software package implementing an event model and loop. |
|
|
4659 | |
|
|
4660 | =item event loop |
|
|
4661 | |
|
|
4662 | An entity that handles and processes external events and converts them |
|
|
4663 | into callback invocations. |
|
|
4664 | |
|
|
4665 | =item event model |
|
|
4666 | |
|
|
4667 | The model used to describe how an event loop handles and processes |
|
|
4668 | watchers and events. |
|
|
4669 | |
|
|
4670 | =item pending |
|
|
4671 | |
|
|
4672 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4673 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4674 | pending status is explicitly cleared by the application. |
|
|
4675 | |
|
|
4676 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4677 | its pending status. |
|
|
4678 | |
|
|
4679 | =item real time |
|
|
4680 | |
|
|
4681 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4682 | |
|
|
4683 | =item wall-clock time |
|
|
4684 | |
|
|
4685 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4686 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4687 | clock. |
|
|
4688 | |
|
|
4689 | =item watcher |
|
|
4690 | |
|
|
4691 | A data structure that describes interest in certain events. Watchers need |
|
|
4692 | to be started (attached to an event loop) before they can receive events. |
|
|
4693 | |
|
|
4694 | =item watcher invocation |
|
|
4695 | |
|
|
4696 | The act of calling the callback associated with a watcher. |
|
|
4697 | |
|
|
4698 | =back |
3188 | |
4699 | |
3189 | =head1 AUTHOR |
4700 | =head1 AUTHOR |
3190 | |
4701 | |
3191 | Marc Lehmann <libev@schmorp.de>. |
4702 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3192 | |
4703 | |