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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 | |
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11 | // a single header file is required |
11 | #include <ev.h> |
12 | #include <ev.h> |
12 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
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16 | // every watcher type has its own typedef'd struct |
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17 | // with the name ev_TYPE |
13 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
15 | |
20 | |
16 | /* called when data readable on stdin */ |
21 | // all watcher callbacks have a similar signature |
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22 | // this callback is called when data is readable on stdin |
17 | static void |
23 | static void |
18 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
19 | { |
25 | { |
20 | /* puts ("stdin ready"); */ |
26 | puts ("stdin ready"); |
21 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
27 | // for one-shot events, one must manually stop the watcher |
22 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
28 | // with its corresponding stop function. |
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29 | ev_io_stop (EV_A_ w); |
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30 | |
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31 | // this causes all nested ev_loop's to stop iterating |
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32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
33 | } |
24 | |
34 | |
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35 | // another callback, this time for a time-out |
25 | static void |
36 | static void |
26 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
27 | { |
38 | { |
28 | /* puts ("timeout"); */ |
39 | puts ("timeout"); |
29 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
40 | // this causes the innermost ev_loop to stop iterating |
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41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
30 | } |
42 | } |
31 | |
43 | |
32 | int |
44 | int |
33 | main (void) |
45 | main (void) |
34 | { |
46 | { |
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47 | // use the default event loop unless you have special needs |
35 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
36 | |
49 | |
37 | /* initialise an io watcher, then start it */ |
50 | // initialise an io watcher, then start it |
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51 | // this one will watch for stdin to become readable |
38 | 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); |
39 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
40 | |
54 | |
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55 | // initialise a timer watcher, then start it |
41 | /* simple non-repeating 5.5 second timeout */ |
56 | // simple non-repeating 5.5 second timeout |
42 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
43 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
44 | |
59 | |
45 | /* loop till timeout or data ready */ |
60 | // now wait for events to arrive |
46 | ev_loop (loop, 0); |
61 | ev_loop (loop, 0); |
47 | |
62 | |
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63 | // unloop was called, so exit |
48 | return 0; |
64 | return 0; |
49 | } |
65 | } |
50 | |
66 | |
51 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
52 | |
68 | |
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69 | This document documents the libev software package. |
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70 | |
53 | The newest version of this document is also available as a html-formatted |
71 | The newest version of this document is also available as an html-formatted |
54 | 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 |
55 | 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 |
56 | |
84 | |
57 | 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 |
58 | 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 |
59 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
60 | |
88 | |
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84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
112 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
113 | for example). |
86 | |
114 | |
87 | =head2 CONVENTIONS |
115 | =head2 CONVENTIONS |
88 | |
116 | |
89 | Libev is very configurable. In this manual the default configuration will |
117 | Libev is very configurable. In this manual the default (and most common) |
90 | be described, which supports multiple event loops. For more info about |
118 | configuration will be described, which supports multiple event loops. For |
91 | various configuration options please have a look at B<EMBED> section in |
119 | more info about various configuration options please have a look at |
92 | this manual. If libev was configured without support for multiple event |
120 | B<EMBED> section in this manual. If libev was configured without support |
93 | loops, then all functions taking an initial argument of name C<loop> |
121 | for multiple event loops, then all functions taking an initial argument of |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
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123 | this argument. |
95 | |
124 | |
96 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
97 | |
126 | |
98 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
102 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
103 | it, you should treat it as some floatingpoint value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
104 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
105 | throughout libev. |
134 | throughout libev. |
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135 | |
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136 | =head1 ERROR HANDLING |
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137 | |
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138 | Libev knows three classes of errors: operating system errors, usage errors |
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139 | and internal errors (bugs). |
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140 | |
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141 | When libev catches an operating system error it cannot handle (for example |
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142 | a system call indicating a condition libev cannot fix), it calls the callback |
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143 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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144 | abort. The default is to print a diagnostic message and to call C<abort |
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145 | ()>. |
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146 | |
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147 | When libev detects a usage error such as a negative timer interval, then |
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148 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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149 | so C<NDEBUG> will disable this checking): these are programming errors in |
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150 | the libev caller and need to be fixed there. |
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151 | |
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152 | Libev also has a few internal error-checking C<assert>ions, and also has |
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153 | extensive consistency checking code. These do not trigger under normal |
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154 | circumstances, as they indicate either a bug in libev or worse. |
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155 | |
106 | |
156 | |
107 | =head1 GLOBAL FUNCTIONS |
157 | =head1 GLOBAL FUNCTIONS |
108 | |
158 | |
109 | These functions can be called anytime, even before initialising the |
159 | These functions can be called anytime, even before initialising the |
110 | library in any way. |
160 | library in any way. |
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119 | |
169 | |
120 | =item ev_sleep (ev_tstamp interval) |
170 | =item ev_sleep (ev_tstamp interval) |
121 | |
171 | |
122 | Sleep for the given interval: The current thread will be blocked until |
172 | Sleep for the given interval: The current thread will be blocked until |
123 | either it is interrupted or the given time interval has passed. Basically |
173 | either it is interrupted or the given time interval has passed. Basically |
124 | this is a subsecond-resolution C<sleep ()>. |
174 | this is a sub-second-resolution C<sleep ()>. |
125 | |
175 | |
126 | =item int ev_version_major () |
176 | =item int ev_version_major () |
127 | |
177 | |
128 | =item int ev_version_minor () |
178 | =item int ev_version_minor () |
129 | |
179 | |
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142 | not a problem. |
192 | not a problem. |
143 | |
193 | |
144 | Example: Make sure we haven't accidentally been linked against the wrong |
194 | Example: Make sure we haven't accidentally been linked against the wrong |
145 | version. |
195 | version. |
146 | |
196 | |
147 | assert (("libev version mismatch", |
197 | assert (("libev version mismatch", |
148 | ev_version_major () == EV_VERSION_MAJOR |
198 | ev_version_major () == EV_VERSION_MAJOR |
149 | && ev_version_minor () >= EV_VERSION_MINOR)); |
199 | && ev_version_minor () >= EV_VERSION_MINOR)); |
150 | |
200 | |
151 | =item unsigned int ev_supported_backends () |
201 | =item unsigned int ev_supported_backends () |
152 | |
202 | |
153 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
203 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
154 | value) compiled into this binary of libev (independent of their |
204 | value) compiled into this binary of libev (independent of their |
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156 | a description of the set values. |
206 | a description of the set values. |
157 | |
207 | |
158 | Example: make sure we have the epoll method, because yeah this is cool and |
208 | Example: make sure we have the epoll method, because yeah this is cool and |
159 | a must have and can we have a torrent of it please!!!11 |
209 | a must have and can we have a torrent of it please!!!11 |
160 | |
210 | |
161 | assert (("sorry, no epoll, no sex", |
211 | assert (("sorry, no epoll, no sex", |
162 | ev_supported_backends () & EVBACKEND_EPOLL)); |
212 | ev_supported_backends () & EVBACKEND_EPOLL)); |
163 | |
213 | |
164 | =item unsigned int ev_recommended_backends () |
214 | =item unsigned int ev_recommended_backends () |
165 | |
215 | |
166 | Return the set of all backends compiled into this binary of libev and also |
216 | Return the set of all backends compiled into this binary of libev and also |
167 | recommended for this platform. This set is often smaller than the one |
217 | recommended for this platform. This set is often smaller than the one |
168 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
218 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
169 | most BSDs and will not be autodetected unless you explicitly request it |
219 | most BSDs and will not be auto-detected unless you explicitly request it |
170 | (assuming you know what you are doing). This is the set of backends that |
220 | (assuming you know what you are doing). This is the set of backends that |
171 | libev will probe for if you specify no backends explicitly. |
221 | libev will probe for if you specify no backends explicitly. |
172 | |
222 | |
173 | =item unsigned int ev_embeddable_backends () |
223 | =item unsigned int ev_embeddable_backends () |
174 | |
224 | |
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178 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
228 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
179 | recommended ones. |
229 | recommended ones. |
180 | |
230 | |
181 | See the description of C<ev_embed> watchers for more info. |
231 | See the description of C<ev_embed> watchers for more info. |
182 | |
232 | |
183 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
233 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
184 | |
234 | |
185 | Sets the allocation function to use (the prototype is similar - the |
235 | Sets the allocation function to use (the prototype is similar - the |
186 | semantics is identical - to the realloc C function). It is used to |
236 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
187 | allocate and free memory (no surprises here). If it returns zero when |
237 | used to allocate and free memory (no surprises here). If it returns zero |
188 | memory needs to be allocated, the library might abort or take some |
238 | when memory needs to be allocated (C<size != 0>), the library might abort |
189 | potentially destructive action. The default is your system realloc |
239 | or take some potentially destructive action. |
190 | function. |
240 | |
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241 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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242 | correct C<realloc> semantics, libev will use a wrapper around the system |
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243 | C<realloc> and C<free> functions by default. |
191 | |
244 | |
192 | You could override this function in high-availability programs to, say, |
245 | You could override this function in high-availability programs to, say, |
193 | free some memory if it cannot allocate memory, to use a special allocator, |
246 | free some memory if it cannot allocate memory, to use a special allocator, |
194 | or even to sleep a while and retry until some memory is available. |
247 | or even to sleep a while and retry until some memory is available. |
195 | |
248 | |
196 | Example: Replace the libev allocator with one that waits a bit and then |
249 | Example: Replace the libev allocator with one that waits a bit and then |
197 | retries). |
250 | retries (example requires a standards-compliant C<realloc>). |
198 | |
251 | |
199 | static void * |
252 | static void * |
200 | persistent_realloc (void *ptr, size_t size) |
253 | persistent_realloc (void *ptr, size_t size) |
201 | { |
254 | { |
202 | for (;;) |
255 | for (;;) |
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211 | } |
264 | } |
212 | |
265 | |
213 | ... |
266 | ... |
214 | ev_set_allocator (persistent_realloc); |
267 | ev_set_allocator (persistent_realloc); |
215 | |
268 | |
216 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
269 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
217 | |
270 | |
218 | Set the callback function to call on a retryable syscall error (such |
271 | Set the callback function to call on a retryable system call error (such |
219 | as failed select, poll, epoll_wait). The message is a printable string |
272 | as failed select, poll, epoll_wait). The message is a printable string |
220 | indicating the system call or subsystem causing the problem. If this |
273 | indicating the system call or subsystem causing the problem. If this |
221 | callback is set, then libev will expect it to remedy the sitution, no |
274 | callback is set, then libev will expect it to remedy the situation, no |
222 | matter what, when it returns. That is, libev will generally retry the |
275 | matter what, when it returns. That is, libev will generally retry the |
223 | requested operation, or, if the condition doesn't go away, do bad stuff |
276 | requested operation, or, if the condition doesn't go away, do bad stuff |
224 | (such as abort). |
277 | (such as abort). |
225 | |
278 | |
226 | Example: This is basically the same thing that libev does internally, too. |
279 | Example: This is basically the same thing that libev does internally, too. |
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237 | |
290 | |
238 | =back |
291 | =back |
239 | |
292 | |
240 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
293 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
241 | |
294 | |
242 | An event loop is described by a C<struct ev_loop *>. The library knows two |
295 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
243 | types of such loops, the I<default> loop, which supports signals and child |
296 | is I<not> optional in this case, as there is also an C<ev_loop> |
244 | events, and dynamically created loops which do not. |
297 | I<function>). |
245 | |
298 | |
246 | If you use threads, a common model is to run the default event loop |
299 | The library knows two types of such loops, the I<default> loop, which |
247 | in your main thread (or in a separate thread) and for each thread you |
300 | supports signals and child events, and dynamically created loops which do |
248 | create, you also create another event loop. Libev itself does no locking |
301 | not. |
249 | whatsoever, so if you mix calls to the same event loop in different |
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250 | threads, make sure you lock (this is usually a bad idea, though, even if |
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251 | done correctly, because it's hideous and inefficient). |
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252 | |
302 | |
253 | =over 4 |
303 | =over 4 |
254 | |
304 | |
255 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
305 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
256 | |
306 | |
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260 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
310 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
261 | |
311 | |
262 | If you don't know what event loop to use, use the one returned from this |
312 | If you don't know what event loop to use, use the one returned from this |
263 | function. |
313 | function. |
264 | |
314 | |
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315 | Note that this function is I<not> thread-safe, so if you want to use it |
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316 | from multiple threads, you have to lock (note also that this is unlikely, |
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317 | as loops cannot be shared easily between threads anyway). |
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318 | |
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319 | The default loop is the only loop that can handle C<ev_signal> and |
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320 | C<ev_child> watchers, and to do this, it always registers a handler |
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321 | for C<SIGCHLD>. If this is a problem for your application you can either |
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322 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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323 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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324 | C<ev_default_init>. |
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325 | |
265 | The flags argument can be used to specify special behaviour or specific |
326 | The flags argument can be used to specify special behaviour or specific |
266 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
327 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
267 | |
328 | |
268 | The following flags are supported: |
329 | The following flags are supported: |
269 | |
330 | |
… | |
… | |
274 | The default flags value. Use this if you have no clue (it's the right |
335 | The default flags value. Use this if you have no clue (it's the right |
275 | thing, believe me). |
336 | thing, believe me). |
276 | |
337 | |
277 | =item C<EVFLAG_NOENV> |
338 | =item C<EVFLAG_NOENV> |
278 | |
339 | |
279 | If this flag bit is ored into the flag value (or the program runs setuid |
340 | If this flag bit is or'ed into the flag value (or the program runs setuid |
280 | or setgid) then libev will I<not> look at the environment variable |
341 | or setgid) then libev will I<not> look at the environment variable |
281 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
342 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
282 | override the flags completely if it is found in the environment. This is |
343 | override the flags completely if it is found in the environment. This is |
283 | useful to try out specific backends to test their performance, or to work |
344 | useful to try out specific backends to test their performance, or to work |
284 | around bugs. |
345 | around bugs. |
… | |
… | |
290 | enabling this flag. |
351 | enabling this flag. |
291 | |
352 | |
292 | This works by calling C<getpid ()> on every iteration of the loop, |
353 | This works by calling C<getpid ()> on every iteration of the loop, |
293 | and thus this might slow down your event loop if you do a lot of loop |
354 | and thus this might slow down your event loop if you do a lot of loop |
294 | iterations and little real work, but is usually not noticeable (on my |
355 | iterations and little real work, but is usually not noticeable (on my |
295 | Linux system for example, C<getpid> is actually a simple 5-insn sequence |
356 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
296 | without a syscall and thus I<very> fast, but my Linux system also has |
357 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
297 | C<pthread_atfork> which is even faster). |
358 | C<pthread_atfork> which is even faster). |
298 | |
359 | |
299 | The big advantage of this flag is that you can forget about fork (and |
360 | The big advantage of this flag is that you can forget about fork (and |
300 | forget about forgetting to tell libev about forking) when you use this |
361 | forget about forgetting to tell libev about forking) when you use this |
301 | flag. |
362 | flag. |
302 | |
363 | |
303 | This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> |
364 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
304 | environment variable. |
365 | environment variable. |
305 | |
366 | |
306 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
307 | |
368 | |
308 | This is your standard select(2) backend. Not I<completely> standard, as |
369 | This is your standard select(2) backend. Not I<completely> standard, as |
… | |
… | |
310 | but if that fails, expect a fairly low limit on the number of fds when |
371 | but if that fails, expect a fairly low limit on the number of fds when |
311 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
372 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
312 | usually the fastest backend for a low number of (low-numbered :) fds. |
373 | usually the fastest backend for a low number of (low-numbered :) fds. |
313 | |
374 | |
314 | To get good performance out of this backend you need a high amount of |
375 | To get good performance out of this backend you need a high amount of |
315 | parallelity (most of the file descriptors should be busy). If you are |
376 | parallelism (most of the file descriptors should be busy). If you are |
316 | writing a server, you should C<accept ()> in a loop to accept as many |
377 | writing a server, you should C<accept ()> in a loop to accept as many |
317 | connections as possible during one iteration. You might also want to have |
378 | connections as possible during one iteration. You might also want to have |
318 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
379 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
319 | readyness notifications you get per iteration. |
380 | readiness notifications you get per iteration. |
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381 | |
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382 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
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383 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
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384 | C<exceptfds> set on that platform). |
320 | |
385 | |
321 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
386 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
322 | |
387 | |
323 | And this is your standard poll(2) backend. It's more complicated |
388 | And this is your standard poll(2) backend. It's more complicated |
324 | than select, but handles sparse fds better and has no artificial |
389 | than select, but handles sparse fds better and has no artificial |
325 | limit on the number of fds you can use (except it will slow down |
390 | limit on the number of fds you can use (except it will slow down |
326 | considerably with a lot of inactive fds). It scales similarly to select, |
391 | considerably with a lot of inactive fds). It scales similarly to select, |
327 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
392 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
328 | performance tips. |
393 | performance tips. |
329 | |
394 | |
|
|
395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
397 | |
330 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
331 | |
399 | |
332 | For few fds, this backend is a bit little slower than poll and select, |
400 | For few fds, this backend is a bit little slower than poll and select, |
333 | but it scales phenomenally better. While poll and select usually scale |
401 | but it scales phenomenally better. While poll and select usually scale |
334 | like O(total_fds) where n is the total number of fds (or the highest fd), |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
335 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
403 | epoll scales either O(1) or O(active_fds). |
336 | of shortcomings, such as silently dropping events in some hard-to-detect |
404 | |
337 | cases and rewiring a syscall per fd change, no fork support and bad |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
338 | support for dup. |
406 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
407 | dropping file descriptors, requiring a system call per change per file |
|
|
408 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
409 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
410 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
411 | take considerable time (one syscall per file descriptor) and is of course |
|
|
412 | hard to detect. |
|
|
413 | |
|
|
414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
415 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
416 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
417 | even remove them from the set) than registered in the set (especially |
|
|
418 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
419 | employing an additional generation counter and comparing that against the |
|
|
420 | events to filter out spurious ones, recreating the set when required. |
339 | |
421 | |
340 | While stopping, setting and starting an I/O watcher in the same iteration |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
341 | will result in some caching, there is still a syscall per such incident |
423 | will result in some caching, there is still a system call per such |
342 | (because the fd could point to a different file description now), so its |
424 | incident (because the same I<file descriptor> could point to a different |
343 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
344 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
345 | |
427 | file descriptors. |
346 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
347 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
348 | (or space) is available. |
|
|
349 | |
428 | |
350 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
351 | watchers for a file descriptor until it has been closed, if possible, i.e. |
430 | watchers for a file descriptor until it has been closed, if possible, |
352 | keep at least one watcher active per fd at all times. |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
432 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
433 | extra overhead. A fork can both result in spurious notifications as well |
|
|
434 | as in libev having to destroy and recreate the epoll object, which can |
|
|
435 | take considerable time and thus should be avoided. |
353 | |
436 | |
|
|
437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
439 | the usage. So sad. |
|
|
440 | |
354 | While nominally embeddeble in other event loops, this feature is broken in |
441 | While nominally embeddable in other event loops, this feature is broken in |
355 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
|
|
443 | |
|
|
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
445 | C<EVBACKEND_POLL>. |
356 | |
446 | |
357 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
358 | |
448 | |
359 | Kqueue deserves special mention, as at the time of this writing, it |
449 | Kqueue deserves special mention, as at the time of this writing, it |
360 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
361 | with anything but sockets and pipes, except on Darwin, where of course |
451 | with anything but sockets and pipes, except on Darwin, where of course |
362 | it's completely useless). For this reason it's not being "autodetected" |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
453 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
454 | without API changes to existing programs. For this reason it's not being |
363 | unless you explicitly specify it explicitly in the flags (i.e. using |
455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
364 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
365 | system like NetBSD. |
457 | system like NetBSD. |
366 | |
458 | |
367 | You still can embed kqueue into a normal poll or select backend and use it |
459 | You still can embed kqueue into a normal poll or select backend and use it |
368 | only for sockets (after having made sure that sockets work with kqueue on |
460 | only for sockets (after having made sure that sockets work with kqueue on |
369 | the target platform). See C<ev_embed> watchers for more info. |
461 | the target platform). See C<ev_embed> watchers for more info. |
370 | |
462 | |
371 | It scales in the same way as the epoll backend, but the interface to the |
463 | It scales in the same way as the epoll backend, but the interface to the |
372 | kernel is more efficient (which says nothing about its actual speed, of |
464 | kernel is more efficient (which says nothing about its actual speed, of |
373 | course). While stopping, setting and starting an I/O watcher does never |
465 | course). While stopping, setting and starting an I/O watcher does never |
374 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
466 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
375 | two event changes per incident, support for C<fork ()> is very bad and it |
467 | two event changes per incident. Support for C<fork ()> is very bad (but |
376 | drops fds silently in similarly hard-to-detect cases. |
468 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
469 | cases |
377 | |
470 | |
378 | This backend usually performs well under most conditions. |
471 | This backend usually performs well under most conditions. |
379 | |
472 | |
380 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
381 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
382 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
383 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
384 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
385 | sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
479 | |
|
|
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
482 | C<NOTE_EOF>. |
386 | |
483 | |
387 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
484 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
388 | |
485 | |
389 | This is not implemented yet (and might never be, unless you send me an |
486 | This is not implemented yet (and might never be, unless you send me an |
390 | implementation). According to reports, C</dev/poll> only supports sockets |
487 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
394 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
491 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
395 | |
492 | |
396 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
493 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
397 | it's really slow, but it still scales very well (O(active_fds)). |
494 | it's really slow, but it still scales very well (O(active_fds)). |
398 | |
495 | |
399 | Please note that solaris event ports can deliver a lot of spurious |
496 | Please note that Solaris event ports can deliver a lot of spurious |
400 | notifications, so you need to use non-blocking I/O or other means to avoid |
497 | notifications, so you need to use non-blocking I/O or other means to avoid |
401 | blocking when no data (or space) is available. |
498 | blocking when no data (or space) is available. |
402 | |
499 | |
403 | While this backend scales well, it requires one system call per active |
500 | While this backend scales well, it requires one system call per active |
404 | file descriptor per loop iteration. For small and medium numbers of file |
501 | file descriptor per loop iteration. For small and medium numbers of file |
405 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
502 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
406 | might perform better. |
503 | might perform better. |
407 | |
504 | |
|
|
505 | On the positive side, with the exception of the spurious readiness |
|
|
506 | notifications, this backend actually performed fully to specification |
|
|
507 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
509 | |
|
|
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
511 | C<EVBACKEND_POLL>. |
|
|
512 | |
408 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
409 | |
514 | |
410 | Try all backends (even potentially broken ones that wouldn't be tried |
515 | Try all backends (even potentially broken ones that wouldn't be tried |
411 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
516 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
412 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
517 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
413 | |
518 | |
414 | It is definitely not recommended to use this flag. |
519 | It is definitely not recommended to use this flag. |
415 | |
520 | |
416 | =back |
521 | =back |
417 | |
522 | |
418 | If one or more of these are ored into the flags value, then only these |
523 | If one or more of these are or'ed into the flags value, then only these |
419 | backends will be tried (in the reverse order as given here). If none are |
524 | backends will be tried (in the reverse order as listed here). If none are |
420 | specified, most compiled-in backend will be tried, usually in reverse |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
421 | order of their flag values :) |
|
|
422 | |
526 | |
423 | The most typical usage is like this: |
527 | Example: This is the most typical usage. |
424 | |
528 | |
425 | if (!ev_default_loop (0)) |
529 | if (!ev_default_loop (0)) |
426 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
427 | |
531 | |
428 | Restrict libev to the select and poll backends, and do not allow |
532 | Example: Restrict libev to the select and poll backends, and do not allow |
429 | environment settings to be taken into account: |
533 | environment settings to be taken into account: |
430 | |
534 | |
431 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
535 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
432 | |
536 | |
433 | Use whatever libev has to offer, but make sure that kqueue is used if |
537 | Example: Use whatever libev has to offer, but make sure that kqueue is |
434 | available (warning, breaks stuff, best use only with your own private |
538 | used if available (warning, breaks stuff, best use only with your own |
435 | event loop and only if you know the OS supports your types of fds): |
539 | private event loop and only if you know the OS supports your types of |
|
|
540 | fds): |
436 | |
541 | |
437 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
542 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
438 | |
543 | |
439 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
544 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
440 | |
545 | |
441 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
546 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
442 | always distinct from the default loop. Unlike the default loop, it cannot |
547 | always distinct from the default loop. Unlike the default loop, it cannot |
443 | handle signal and child watchers, and attempts to do so will be greeted by |
548 | handle signal and child watchers, and attempts to do so will be greeted by |
444 | undefined behaviour (or a failed assertion if assertions are enabled). |
549 | undefined behaviour (or a failed assertion if assertions are enabled). |
445 | |
550 | |
|
|
551 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
552 | libev with threads is indeed to create one loop per thread, and using the |
|
|
553 | default loop in the "main" or "initial" thread. |
|
|
554 | |
446 | Example: Try to create a event loop that uses epoll and nothing else. |
555 | Example: Try to create a event loop that uses epoll and nothing else. |
447 | |
556 | |
448 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
557 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
449 | if (!epoller) |
558 | if (!epoller) |
450 | fatal ("no epoll found here, maybe it hides under your chair"); |
559 | fatal ("no epoll found here, maybe it hides under your chair"); |
451 | |
560 | |
452 | =item ev_default_destroy () |
561 | =item ev_default_destroy () |
453 | |
562 | |
454 | Destroys the default loop again (frees all memory and kernel state |
563 | Destroys the default loop again (frees all memory and kernel state |
455 | etc.). None of the active event watchers will be stopped in the normal |
564 | etc.). None of the active event watchers will be stopped in the normal |
456 | sense, so e.g. C<ev_is_active> might still return true. It is your |
565 | sense, so e.g. C<ev_is_active> might still return true. It is your |
457 | responsibility to either stop all watchers cleanly yoursef I<before> |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
458 | calling this function, or cope with the fact afterwards (which is usually |
567 | calling this function, or cope with the fact afterwards (which is usually |
459 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
568 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
460 | for example). |
569 | for example). |
461 | |
570 | |
462 | Note that certain global state, such as signal state, will not be freed by |
571 | Note that certain global state, such as signal state (and installed signal |
463 | this function, and related watchers (such as signal and child watchers) |
572 | handlers), will not be freed by this function, and related watchers (such |
464 | would need to be stopped manually. |
573 | as signal and child watchers) would need to be stopped manually. |
465 | |
574 | |
466 | In general it is not advisable to call this function except in the |
575 | In general it is not advisable to call this function except in the |
467 | rare occasion where you really need to free e.g. the signal handling |
576 | rare occasion where you really need to free e.g. the signal handling |
468 | pipe fds. If you need dynamically allocated loops it is better to use |
577 | pipe fds. If you need dynamically allocated loops it is better to use |
469 | C<ev_loop_new> and C<ev_loop_destroy>). |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
473 | Like C<ev_default_destroy>, but destroys an event loop created by an |
582 | Like C<ev_default_destroy>, but destroys an event loop created by an |
474 | earlier call to C<ev_loop_new>. |
583 | earlier call to C<ev_loop_new>. |
475 | |
584 | |
476 | =item ev_default_fork () |
585 | =item ev_default_fork () |
477 | |
586 | |
|
|
587 | This function sets a flag that causes subsequent C<ev_loop> iterations |
478 | This function reinitialises the kernel state for backends that have |
588 | to reinitialise the kernel state for backends that have one. Despite the |
479 | one. Despite the name, you can call it anytime, but it makes most sense |
589 | name, you can call it anytime, but it makes most sense after forking, in |
480 | after forking, in either the parent or child process (or both, but that |
590 | the child process (or both child and parent, but that again makes little |
481 | again makes little sense). |
591 | sense). You I<must> call it in the child before using any of the libev |
|
|
592 | functions, and it will only take effect at the next C<ev_loop> iteration. |
482 | |
593 | |
483 | You I<must> call this function in the child process after forking if and |
594 | On the other hand, you only need to call this function in the child |
484 | only if you want to use the event library in both processes. If you just |
595 | process if and only if you want to use the event library in the child. If |
485 | fork+exec, you don't have to call it. |
596 | you just fork+exec, you don't have to call it at all. |
486 | |
597 | |
487 | The function itself is quite fast and it's usually not a problem to call |
598 | The function itself is quite fast and it's usually not a problem to call |
488 | it just in case after a fork. To make this easy, the function will fit in |
599 | it just in case after a fork. To make this easy, the function will fit in |
489 | quite nicely into a call to C<pthread_atfork>: |
600 | quite nicely into a call to C<pthread_atfork>: |
490 | |
601 | |
491 | pthread_atfork (0, 0, ev_default_fork); |
602 | pthread_atfork (0, 0, ev_default_fork); |
492 | |
603 | |
493 | At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
|
|
494 | without calling this function, so if you force one of those backends you |
|
|
495 | do not need to care. |
|
|
496 | |
|
|
497 | =item ev_loop_fork (loop) |
604 | =item ev_loop_fork (loop) |
498 | |
605 | |
499 | Like C<ev_default_fork>, but acts on an event loop created by |
606 | Like C<ev_default_fork>, but acts on an event loop created by |
500 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
607 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
501 | after fork, and how you do this is entirely your own problem. |
608 | after fork that you want to re-use in the child, and how you do this is |
|
|
609 | entirely your own problem. |
|
|
610 | |
|
|
611 | =item int ev_is_default_loop (loop) |
|
|
612 | |
|
|
613 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
614 | otherwise. |
502 | |
615 | |
503 | =item unsigned int ev_loop_count (loop) |
616 | =item unsigned int ev_loop_count (loop) |
504 | |
617 | |
505 | Returns the count of loop iterations for the loop, which is identical to |
618 | Returns the count of loop iterations for the loop, which is identical to |
506 | the number of times libev did poll for new events. It starts at C<0> and |
619 | the number of times libev did poll for new events. It starts at C<0> and |
507 | happily wraps around with enough iterations. |
620 | happily wraps around with enough iterations. |
508 | |
621 | |
509 | This value can sometimes be useful as a generation counter of sorts (it |
622 | This value can sometimes be useful as a generation counter of sorts (it |
510 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
511 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
|
|
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
512 | |
637 | |
513 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
514 | |
639 | |
515 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
516 | use. |
641 | use. |
… | |
… | |
521 | received events and started processing them. This timestamp does not |
646 | received events and started processing them. This timestamp does not |
522 | change as long as callbacks are being processed, and this is also the base |
647 | change as long as callbacks are being processed, and this is also the base |
523 | time used for relative timers. You can treat it as the timestamp of the |
648 | time used for relative timers. You can treat it as the timestamp of the |
524 | event occurring (or more correctly, libev finding out about it). |
649 | event occurring (or more correctly, libev finding out about it). |
525 | |
650 | |
|
|
651 | =item ev_now_update (loop) |
|
|
652 | |
|
|
653 | Establishes the current time by querying the kernel, updating the time |
|
|
654 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
655 | is usually done automatically within C<ev_loop ()>. |
|
|
656 | |
|
|
657 | This function is rarely useful, but when some event callback runs for a |
|
|
658 | very long time without entering the event loop, updating libev's idea of |
|
|
659 | the current time is a good idea. |
|
|
660 | |
|
|
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
662 | |
|
|
663 | =item ev_suspend (loop) |
|
|
664 | |
|
|
665 | =item ev_resume (loop) |
|
|
666 | |
|
|
667 | These two functions suspend and resume a loop, for use when the loop is |
|
|
668 | not used for a while and timeouts should not be processed. |
|
|
669 | |
|
|
670 | A typical use case would be an interactive program such as a game: When |
|
|
671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
672 | would be best to handle timeouts as if no time had actually passed while |
|
|
673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
675 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
676 | |
|
|
677 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
678 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
679 | will be rescheduled (that is, they will lose any events that would have |
|
|
680 | occured while suspended). |
|
|
681 | |
|
|
682 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
683 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
684 | without a previous call to C<ev_suspend>. |
|
|
685 | |
|
|
686 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
687 | event loop time (see C<ev_now_update>). |
|
|
688 | |
526 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
527 | |
690 | |
528 | Finally, this is it, the event handler. This function usually is called |
691 | Finally, this is it, the event handler. This function usually is called |
529 | after you initialised all your watchers and you want to start handling |
692 | after you initialised all your watchers and you want to start handling |
530 | events. |
693 | events. |
… | |
… | |
532 | If the flags argument is specified as C<0>, it will not return until |
695 | If the flags argument is specified as C<0>, it will not return until |
533 | either no event watchers are active anymore or C<ev_unloop> was called. |
696 | either no event watchers are active anymore or C<ev_unloop> was called. |
534 | |
697 | |
535 | Please note that an explicit C<ev_unloop> is usually better than |
698 | Please note that an explicit C<ev_unloop> is usually better than |
536 | relying on all watchers to be stopped when deciding when a program has |
699 | relying on all watchers to be stopped when deciding when a program has |
537 | finished (especially in interactive programs), but having a program that |
700 | finished (especially in interactive programs), but having a program |
538 | automatically loops as long as it has to and no longer by virtue of |
701 | that automatically loops as long as it has to and no longer by virtue |
539 | relying on its watchers stopping correctly is a thing of beauty. |
702 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
703 | beauty. |
540 | |
704 | |
541 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
705 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
542 | those events and any outstanding ones, but will not block your process in |
706 | those events and any already outstanding ones, but will not block your |
543 | case there are no events and will return after one iteration of the loop. |
707 | process in case there are no events and will return after one iteration of |
|
|
708 | the loop. |
544 | |
709 | |
545 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
710 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
546 | neccessary) and will handle those and any outstanding ones. It will block |
711 | necessary) and will handle those and any already outstanding ones. It |
547 | your process until at least one new event arrives, and will return after |
712 | will block your process until at least one new event arrives (which could |
548 | one iteration of the loop. This is useful if you are waiting for some |
713 | be an event internal to libev itself, so there is no guarantee that a |
549 | external event in conjunction with something not expressible using other |
714 | user-registered callback will be called), and will return after one |
|
|
715 | iteration of the loop. |
|
|
716 | |
|
|
717 | This is useful if you are waiting for some external event in conjunction |
|
|
718 | with something not expressible using other libev watchers (i.e. "roll your |
550 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
719 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
551 | usually a better approach for this kind of thing. |
720 | usually a better approach for this kind of thing. |
552 | |
721 | |
553 | Here are the gory details of what C<ev_loop> does: |
722 | Here are the gory details of what C<ev_loop> does: |
554 | |
723 | |
555 | - Before the first iteration, call any pending watchers. |
724 | - Before the first iteration, call any pending watchers. |
556 | * If EVFLAG_FORKCHECK was used, check for a fork. |
725 | * If EVFLAG_FORKCHECK was used, check for a fork. |
557 | - If a fork was detected, queue and call all fork watchers. |
726 | - If a fork was detected (by any means), queue and call all fork watchers. |
558 | - Queue and call all prepare watchers. |
727 | - Queue and call all prepare watchers. |
559 | - If we have been forked, recreate the kernel state. |
728 | - If we have been forked, detach and recreate the kernel state |
|
|
729 | as to not disturb the other process. |
560 | - Update the kernel state with all outstanding changes. |
730 | - Update the kernel state with all outstanding changes. |
561 | - Update the "event loop time". |
731 | - Update the "event loop time" (ev_now ()). |
562 | - Calculate for how long to sleep or block, if at all |
732 | - Calculate for how long to sleep or block, if at all |
563 | (active idle watchers, EVLOOP_NONBLOCK or not having |
733 | (active idle watchers, EVLOOP_NONBLOCK or not having |
564 | any active watchers at all will result in not sleeping). |
734 | any active watchers at all will result in not sleeping). |
565 | - Sleep if the I/O and timer collect interval say so. |
735 | - Sleep if the I/O and timer collect interval say so. |
566 | - Block the process, waiting for any events. |
736 | - Block the process, waiting for any events. |
567 | - Queue all outstanding I/O (fd) events. |
737 | - Queue all outstanding I/O (fd) events. |
568 | - Update the "event loop time" and do time jump handling. |
738 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
569 | - Queue all outstanding timers. |
739 | - Queue all expired timers. |
570 | - Queue all outstanding periodics. |
740 | - Queue all expired periodics. |
571 | - If no events are pending now, queue all idle watchers. |
741 | - Unless any events are pending now, queue all idle watchers. |
572 | - Queue all check watchers. |
742 | - Queue all check watchers. |
573 | - Call all queued watchers in reverse order (i.e. check watchers first). |
743 | - Call all queued watchers in reverse order (i.e. check watchers first). |
574 | Signals and child watchers are implemented as I/O watchers, and will |
744 | Signals and child watchers are implemented as I/O watchers, and will |
575 | be handled here by queueing them when their watcher gets executed. |
745 | be handled here by queueing them when their watcher gets executed. |
576 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
746 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
… | |
… | |
581 | anymore. |
751 | anymore. |
582 | |
752 | |
583 | ... queue jobs here, make sure they register event watchers as long |
753 | ... queue jobs here, make sure they register event watchers as long |
584 | ... as they still have work to do (even an idle watcher will do..) |
754 | ... as they still have work to do (even an idle watcher will do..) |
585 | ev_loop (my_loop, 0); |
755 | ev_loop (my_loop, 0); |
586 | ... jobs done. yeah! |
756 | ... jobs done or somebody called unloop. yeah! |
587 | |
757 | |
588 | =item ev_unloop (loop, how) |
758 | =item ev_unloop (loop, how) |
589 | |
759 | |
590 | Can be used to make a call to C<ev_loop> return early (but only after it |
760 | Can be used to make a call to C<ev_loop> return early (but only after it |
591 | has processed all outstanding events). The C<how> argument must be either |
761 | has processed all outstanding events). The C<how> argument must be either |
592 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
762 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
593 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
763 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
594 | |
764 | |
|
|
765 | This "unloop state" will be cleared when entering C<ev_loop> again. |
|
|
766 | |
|
|
767 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
768 | |
595 | =item ev_ref (loop) |
769 | =item ev_ref (loop) |
596 | |
770 | |
597 | =item ev_unref (loop) |
771 | =item ev_unref (loop) |
598 | |
772 | |
599 | Ref/unref can be used to add or remove a reference count on the event |
773 | Ref/unref can be used to add or remove a reference count on the event |
600 | loop: Every watcher keeps one reference, and as long as the reference |
774 | loop: Every watcher keeps one reference, and as long as the reference |
601 | count is nonzero, C<ev_loop> will not return on its own. If you have |
775 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
776 | |
602 | a watcher you never unregister that should not keep C<ev_loop> from |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
603 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
779 | stopping it. |
|
|
780 | |
604 | example, libev itself uses this for its internal signal pipe: It is not |
781 | As an example, libev itself uses this for its internal signal pipe: It |
605 | visible to the libev user and should not keep C<ev_loop> from exiting if |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
606 | no event watchers registered by it are active. It is also an excellent |
783 | exiting if no event watchers registered by it are active. It is also an |
607 | way to do this for generic recurring timers or from within third-party |
784 | excellent way to do this for generic recurring timers or from within |
608 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
785 | third-party libraries. Just remember to I<unref after start> and I<ref |
|
|
786 | before stop> (but only if the watcher wasn't active before, or was active |
|
|
787 | before, respectively. Note also that libev might stop watchers itself |
|
|
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
789 | in the callback). |
609 | |
790 | |
610 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
611 | running when nothing else is active. |
792 | running when nothing else is active. |
612 | |
793 | |
613 | struct ev_signal exitsig; |
794 | ev_signal exitsig; |
614 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
795 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
615 | ev_signal_start (loop, &exitsig); |
796 | ev_signal_start (loop, &exitsig); |
616 | evf_unref (loop); |
797 | evf_unref (loop); |
617 | |
798 | |
618 | Example: For some weird reason, unregister the above signal handler again. |
799 | Example: For some weird reason, unregister the above signal handler again. |
619 | |
800 | |
620 | ev_ref (loop); |
801 | ev_ref (loop); |
621 | ev_signal_stop (loop, &exitsig); |
802 | ev_signal_stop (loop, &exitsig); |
622 | |
803 | |
623 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
804 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
624 | |
805 | |
625 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
806 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
626 | |
807 | |
627 | These advanced functions influence the time that libev will spend waiting |
808 | These advanced functions influence the time that libev will spend waiting |
628 | for events. Both are by default C<0>, meaning that libev will try to |
809 | for events. Both time intervals are by default C<0>, meaning that libev |
629 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
810 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
811 | latency. |
630 | |
812 | |
631 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
813 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
632 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
814 | allows libev to delay invocation of I/O and timer/periodic callbacks |
633 | increase efficiency of loop iterations. |
815 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
816 | opportunities). |
634 | |
817 | |
635 | The background is that sometimes your program runs just fast enough to |
818 | The idea is that sometimes your program runs just fast enough to handle |
636 | handle one (or very few) event(s) per loop iteration. While this makes |
819 | one (or very few) event(s) per loop iteration. While this makes the |
637 | the program responsive, it also wastes a lot of CPU time to poll for new |
820 | program responsive, it also wastes a lot of CPU time to poll for new |
638 | events, especially with backends like C<select ()> which have a high |
821 | events, especially with backends like C<select ()> which have a high |
639 | overhead for the actual polling but can deliver many events at once. |
822 | overhead for the actual polling but can deliver many events at once. |
640 | |
823 | |
641 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
642 | time collecting I/O events, so you can handle more events per iteration, |
825 | time collecting I/O events, so you can handle more events per iteration, |
643 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
644 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
645 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
646 | |
831 | |
647 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
648 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
649 | latency (the watcher callback will be called later). C<ev_io> watchers |
834 | latency/jitter/inexactness (the watcher callback will be called |
650 | will not be affected. Setting this to a non-null value will not introduce |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
651 | any overhead in libev. |
836 | value will not introduce any overhead in libev. |
652 | |
837 | |
653 | Many (busy) programs can usually benefit by setting the io collect |
838 | Many (busy) programs can usually benefit by setting the I/O collect |
654 | interval to a value near C<0.1> or so, which is often enough for |
839 | interval to a value near C<0.1> or so, which is often enough for |
655 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
656 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
657 | as this approsaches the timing granularity of most systems. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
|
|
847 | |
|
|
848 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
849 | saving power, as the program will "bundle" timer callback invocations that |
|
|
850 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
851 | times the process sleeps and wakes up again. Another useful technique to |
|
|
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
853 | they fire on, say, one-second boundaries only. |
|
|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
|
857 | |
|
|
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
860 | |
|
|
861 | =item ev_loop_verify (loop) |
|
|
862 | |
|
|
863 | This function only does something when C<EV_VERIFY> support has been |
|
|
864 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
865 | through all internal structures and checks them for validity. If anything |
|
|
866 | is found to be inconsistent, it will print an error message to standard |
|
|
867 | error and call C<abort ()>. |
|
|
868 | |
|
|
869 | This can be used to catch bugs inside libev itself: under normal |
|
|
870 | circumstances, this function will never abort as of course libev keeps its |
|
|
871 | data structures consistent. |
658 | |
872 | |
659 | =back |
873 | =back |
660 | |
874 | |
661 | |
875 | |
662 | =head1 ANATOMY OF A WATCHER |
876 | =head1 ANATOMY OF A WATCHER |
|
|
877 | |
|
|
878 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
879 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
880 | watchers and C<ev_io_start> for I/O watchers. |
663 | |
881 | |
664 | A watcher is a structure that you create and register to record your |
882 | A watcher is a structure that you create and register to record your |
665 | interest in some event. For instance, if you want to wait for STDIN to |
883 | interest in some event. For instance, if you want to wait for STDIN to |
666 | become readable, you would create an C<ev_io> watcher for that: |
884 | become readable, you would create an C<ev_io> watcher for that: |
667 | |
885 | |
668 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
886 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
669 | { |
887 | { |
670 | ev_io_stop (w); |
888 | ev_io_stop (w); |
671 | ev_unloop (loop, EVUNLOOP_ALL); |
889 | ev_unloop (loop, EVUNLOOP_ALL); |
672 | } |
890 | } |
673 | |
891 | |
674 | struct ev_loop *loop = ev_default_loop (0); |
892 | struct ev_loop *loop = ev_default_loop (0); |
|
|
893 | |
675 | struct ev_io stdin_watcher; |
894 | ev_io stdin_watcher; |
|
|
895 | |
676 | ev_init (&stdin_watcher, my_cb); |
896 | ev_init (&stdin_watcher, my_cb); |
677 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
897 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
678 | ev_io_start (loop, &stdin_watcher); |
898 | ev_io_start (loop, &stdin_watcher); |
|
|
899 | |
679 | ev_loop (loop, 0); |
900 | ev_loop (loop, 0); |
680 | |
901 | |
681 | As you can see, you are responsible for allocating the memory for your |
902 | As you can see, you are responsible for allocating the memory for your |
682 | watcher structures (and it is usually a bad idea to do this on the stack, |
903 | watcher structures (and it is I<usually> a bad idea to do this on the |
683 | although this can sometimes be quite valid). |
904 | stack). |
|
|
905 | |
|
|
906 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
907 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
684 | |
908 | |
685 | Each watcher structure must be initialised by a call to C<ev_init |
909 | Each watcher structure must be initialised by a call to C<ev_init |
686 | (watcher *, callback)>, which expects a callback to be provided. This |
910 | (watcher *, callback)>, which expects a callback to be provided. This |
687 | callback gets invoked each time the event occurs (or, in the case of io |
911 | callback gets invoked each time the event occurs (or, in the case of I/O |
688 | watchers, each time the event loop detects that the file descriptor given |
912 | watchers, each time the event loop detects that the file descriptor given |
689 | is readable and/or writable). |
913 | is readable and/or writable). |
690 | |
914 | |
691 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
915 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
692 | with arguments specific to this watcher type. There is also a macro |
916 | macro to configure it, with arguments specific to the watcher type. There |
693 | to combine initialisation and setting in one call: C<< ev_<type>_init |
917 | is also a macro to combine initialisation and setting in one call: C<< |
694 | (watcher *, callback, ...) >>. |
918 | ev_TYPE_init (watcher *, callback, ...) >>. |
695 | |
919 | |
696 | To make the watcher actually watch out for events, you have to start it |
920 | To make the watcher actually watch out for events, you have to start it |
697 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
921 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
698 | *) >>), and you can stop watching for events at any time by calling the |
922 | *) >>), and you can stop watching for events at any time by calling the |
699 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
923 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
700 | |
924 | |
701 | As long as your watcher is active (has been started but not stopped) you |
925 | As long as your watcher is active (has been started but not stopped) you |
702 | must not touch the values stored in it. Most specifically you must never |
926 | must not touch the values stored in it. Most specifically you must never |
703 | reinitialise it or call its C<set> macro. |
927 | reinitialise it or call its C<ev_TYPE_set> macro. |
704 | |
928 | |
705 | Each and every callback receives the event loop pointer as first, the |
929 | Each and every callback receives the event loop pointer as first, the |
706 | registered watcher structure as second, and a bitset of received events as |
930 | registered watcher structure as second, and a bitset of received events as |
707 | third argument. |
931 | third argument. |
708 | |
932 | |
… | |
… | |
762 | =item C<EV_FORK> |
986 | =item C<EV_FORK> |
763 | |
987 | |
764 | The event loop has been resumed in the child process after fork (see |
988 | The event loop has been resumed in the child process after fork (see |
765 | C<ev_fork>). |
989 | C<ev_fork>). |
766 | |
990 | |
|
|
991 | =item C<EV_ASYNC> |
|
|
992 | |
|
|
993 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
994 | |
|
|
995 | =item C<EV_CUSTOM> |
|
|
996 | |
|
|
997 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
998 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
999 | |
767 | =item C<EV_ERROR> |
1000 | =item C<EV_ERROR> |
768 | |
1001 | |
769 | An unspecified error has occured, the watcher has been stopped. This might |
1002 | An unspecified error has occurred, the watcher has been stopped. This might |
770 | happen because the watcher could not be properly started because libev |
1003 | happen because the watcher could not be properly started because libev |
771 | ran out of memory, a file descriptor was found to be closed or any other |
1004 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1005 | problem. Libev considers these application bugs. |
|
|
1006 | |
772 | problem. You best act on it by reporting the problem and somehow coping |
1007 | You best act on it by reporting the problem and somehow coping with the |
773 | with the watcher being stopped. |
1008 | watcher being stopped. Note that well-written programs should not receive |
|
|
1009 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1010 | bug in your program. |
774 | |
1011 | |
775 | Libev will usually signal a few "dummy" events together with an error, |
1012 | Libev will usually signal a few "dummy" events together with an error, for |
776 | for example it might indicate that a fd is readable or writable, and if |
1013 | example it might indicate that a fd is readable or writable, and if your |
777 | your callbacks is well-written it can just attempt the operation and cope |
1014 | callbacks is well-written it can just attempt the operation and cope with |
778 | with the error from read() or write(). This will not work in multithreaded |
1015 | the error from read() or write(). This will not work in multi-threaded |
779 | programs, though, so beware. |
1016 | programs, though, as the fd could already be closed and reused for another |
|
|
1017 | thing, so beware. |
780 | |
1018 | |
781 | =back |
1019 | =back |
782 | |
1020 | |
783 | =head2 GENERIC WATCHER FUNCTIONS |
1021 | =head2 GENERIC WATCHER FUNCTIONS |
784 | |
|
|
785 | In the following description, C<TYPE> stands for the watcher type, |
|
|
786 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
787 | |
1022 | |
788 | =over 4 |
1023 | =over 4 |
789 | |
1024 | |
790 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1025 | =item C<ev_init> (ev_TYPE *watcher, callback) |
791 | |
1026 | |
… | |
… | |
797 | which rolls both calls into one. |
1032 | which rolls both calls into one. |
798 | |
1033 | |
799 | You can reinitialise a watcher at any time as long as it has been stopped |
1034 | You can reinitialise a watcher at any time as long as it has been stopped |
800 | (or never started) and there are no pending events outstanding. |
1035 | (or never started) and there are no pending events outstanding. |
801 | |
1036 | |
802 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1037 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
803 | int revents)>. |
1038 | int revents)>. |
|
|
1039 | |
|
|
1040 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1041 | |
|
|
1042 | ev_io w; |
|
|
1043 | ev_init (&w, my_cb); |
|
|
1044 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
804 | |
1045 | |
805 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1046 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
806 | |
1047 | |
807 | This macro initialises the type-specific parts of a watcher. You need to |
1048 | This macro initialises the type-specific parts of a watcher. You need to |
808 | call C<ev_init> at least once before you call this macro, but you can |
1049 | call C<ev_init> at least once before you call this macro, but you can |
… | |
… | |
811 | difference to the C<ev_init> macro). |
1052 | difference to the C<ev_init> macro). |
812 | |
1053 | |
813 | Although some watcher types do not have type-specific arguments |
1054 | Although some watcher types do not have type-specific arguments |
814 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1055 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
815 | |
1056 | |
|
|
1057 | See C<ev_init>, above, for an example. |
|
|
1058 | |
816 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1059 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
817 | |
1060 | |
818 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1061 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
819 | calls into a single call. This is the most convinient method to initialise |
1062 | calls into a single call. This is the most convenient method to initialise |
820 | a watcher. The same limitations apply, of course. |
1063 | a watcher. The same limitations apply, of course. |
|
|
1064 | |
|
|
1065 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1066 | |
|
|
1067 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
821 | |
1068 | |
822 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1069 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
823 | |
1070 | |
824 | Starts (activates) the given watcher. Only active watchers will receive |
1071 | Starts (activates) the given watcher. Only active watchers will receive |
825 | events. If the watcher is already active nothing will happen. |
1072 | events. If the watcher is already active nothing will happen. |
826 | |
1073 | |
|
|
1074 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1075 | whole section. |
|
|
1076 | |
|
|
1077 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1078 | |
827 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1079 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
828 | |
1080 | |
829 | Stops the given watcher again (if active) and clears the pending |
1081 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1082 | the watcher was active or not). |
|
|
1083 | |
830 | status. It is possible that stopped watchers are pending (for example, |
1084 | It is possible that stopped watchers are pending - for example, |
831 | non-repeating timers are being stopped when they become pending), but |
1085 | non-repeating timers are being stopped when they become pending - but |
832 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1086 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
833 | you want to free or reuse the memory used by the watcher it is therefore a |
1087 | pending. If you want to free or reuse the memory used by the watcher it is |
834 | good idea to always call its C<ev_TYPE_stop> function. |
1088 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
835 | |
1089 | |
836 | =item bool ev_is_active (ev_TYPE *watcher) |
1090 | =item bool ev_is_active (ev_TYPE *watcher) |
837 | |
1091 | |
838 | Returns a true value iff the watcher is active (i.e. it has been started |
1092 | Returns a true value iff the watcher is active (i.e. it has been started |
839 | and not yet been stopped). As long as a watcher is active you must not modify |
1093 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
865 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1119 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
866 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1120 | (default: C<-2>). Pending watchers with higher priority will be invoked |
867 | before watchers with lower priority, but priority will not keep watchers |
1121 | before watchers with lower priority, but priority will not keep watchers |
868 | from being executed (except for C<ev_idle> watchers). |
1122 | from being executed (except for C<ev_idle> watchers). |
869 | |
1123 | |
870 | This means that priorities are I<only> used for ordering callback |
|
|
871 | invocation after new events have been received. This is useful, for |
|
|
872 | example, to reduce latency after idling, or more often, to bind two |
|
|
873 | watchers on the same event and make sure one is called first. |
|
|
874 | |
|
|
875 | If you need to suppress invocation when higher priority events are pending |
1124 | If you need to suppress invocation when higher priority events are pending |
876 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1125 | you need to look at C<ev_idle> watchers, which provide this functionality. |
877 | |
1126 | |
878 | You I<must not> change the priority of a watcher as long as it is active or |
1127 | You I<must not> change the priority of a watcher as long as it is active or |
879 | pending. |
1128 | pending. |
880 | |
1129 | |
|
|
1130 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1131 | fine, as long as you do not mind that the priority value you query might |
|
|
1132 | or might not have been clamped to the valid range. |
|
|
1133 | |
881 | The default priority used by watchers when no priority has been set is |
1134 | The default priority used by watchers when no priority has been set is |
882 | always C<0>, which is supposed to not be too high and not be too low :). |
1135 | always C<0>, which is supposed to not be too high and not be too low :). |
883 | |
1136 | |
884 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1137 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
885 | fine, as long as you do not mind that the priority value you query might |
1138 | priorities. |
886 | or might not have been adjusted to be within valid range. |
|
|
887 | |
1139 | |
888 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1140 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
889 | |
1141 | |
890 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1142 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
891 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1143 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
892 | can deal with that fact. |
1144 | can deal with that fact, as both are simply passed through to the |
|
|
1145 | callback. |
893 | |
1146 | |
894 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1147 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
895 | |
1148 | |
896 | If the watcher is pending, this function returns clears its pending status |
1149 | If the watcher is pending, this function clears its pending status and |
897 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1150 | returns its C<revents> bitset (as if its callback was invoked). If the |
898 | watcher isn't pending it does nothing and returns C<0>. |
1151 | watcher isn't pending it does nothing and returns C<0>. |
899 | |
1152 | |
|
|
1153 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1154 | callback to be invoked, which can be accomplished with this function. |
|
|
1155 | |
900 | =back |
1156 | =back |
901 | |
1157 | |
902 | |
1158 | |
903 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1159 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
904 | |
1160 | |
905 | Each watcher has, by default, a member C<void *data> that you can change |
1161 | Each watcher has, by default, a member C<void *data> that you can change |
906 | and read at any time, libev will completely ignore it. This can be used |
1162 | and read at any time: libev will completely ignore it. This can be used |
907 | to associate arbitrary data with your watcher. If you need more data and |
1163 | to associate arbitrary data with your watcher. If you need more data and |
908 | don't want to allocate memory and store a pointer to it in that data |
1164 | don't want to allocate memory and store a pointer to it in that data |
909 | member, you can also "subclass" the watcher type and provide your own |
1165 | member, you can also "subclass" the watcher type and provide your own |
910 | data: |
1166 | data: |
911 | |
1167 | |
912 | struct my_io |
1168 | struct my_io |
913 | { |
1169 | { |
914 | struct ev_io io; |
1170 | ev_io io; |
915 | int otherfd; |
1171 | int otherfd; |
916 | void *somedata; |
1172 | void *somedata; |
917 | struct whatever *mostinteresting; |
1173 | struct whatever *mostinteresting; |
918 | } |
1174 | }; |
|
|
1175 | |
|
|
1176 | ... |
|
|
1177 | struct my_io w; |
|
|
1178 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
919 | |
1179 | |
920 | And since your callback will be called with a pointer to the watcher, you |
1180 | And since your callback will be called with a pointer to the watcher, you |
921 | can cast it back to your own type: |
1181 | can cast it back to your own type: |
922 | |
1182 | |
923 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1183 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
924 | { |
1184 | { |
925 | struct my_io *w = (struct my_io *)w_; |
1185 | struct my_io *w = (struct my_io *)w_; |
926 | ... |
1186 | ... |
927 | } |
1187 | } |
928 | |
1188 | |
929 | More interesting and less C-conformant ways of casting your callback type |
1189 | More interesting and less C-conformant ways of casting your callback type |
930 | instead have been omitted. |
1190 | instead have been omitted. |
931 | |
1191 | |
932 | Another common scenario is having some data structure with multiple |
1192 | Another common scenario is to use some data structure with multiple |
933 | watchers: |
1193 | embedded watchers: |
934 | |
1194 | |
935 | struct my_biggy |
1195 | struct my_biggy |
936 | { |
1196 | { |
937 | int some_data; |
1197 | int some_data; |
938 | ev_timer t1; |
1198 | ev_timer t1; |
939 | ev_timer t2; |
1199 | ev_timer t2; |
940 | } |
1200 | } |
941 | |
1201 | |
942 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1202 | In this case getting the pointer to C<my_biggy> is a bit more |
943 | you need to use C<offsetof>: |
1203 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1204 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1205 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1206 | programmers): |
944 | |
1207 | |
945 | #include <stddef.h> |
1208 | #include <stddef.h> |
946 | |
1209 | |
947 | static void |
1210 | static void |
948 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1211 | t1_cb (EV_P_ ev_timer *w, int revents) |
949 | { |
1212 | { |
950 | struct my_biggy big = (struct my_biggy * |
1213 | struct my_biggy big = (struct my_biggy *) |
951 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1214 | (((char *)w) - offsetof (struct my_biggy, t1)); |
952 | } |
1215 | } |
953 | |
1216 | |
954 | static void |
1217 | static void |
955 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1218 | t2_cb (EV_P_ ev_timer *w, int revents) |
956 | { |
1219 | { |
957 | struct my_biggy big = (struct my_biggy * |
1220 | struct my_biggy big = (struct my_biggy *) |
958 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1221 | (((char *)w) - offsetof (struct my_biggy, t2)); |
959 | } |
1222 | } |
|
|
1223 | |
|
|
1224 | =head2 WATCHER PRIORITY MODELS |
|
|
1225 | |
|
|
1226 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1227 | integers that influence the ordering of event callback invocation |
|
|
1228 | between watchers in some way, all else being equal. |
|
|
1229 | |
|
|
1230 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1231 | description for the more technical details such as the actual priority |
|
|
1232 | range. |
|
|
1233 | |
|
|
1234 | There are two common ways how these these priorities are being interpreted |
|
|
1235 | by event loops: |
|
|
1236 | |
|
|
1237 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1238 | of lower priority watchers, which means as long as higher priority |
|
|
1239 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1240 | |
|
|
1241 | The less common only-for-ordering model uses priorities solely to order |
|
|
1242 | callback invocation within a single event loop iteration: Higher priority |
|
|
1243 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1244 | before polling for new events. |
|
|
1245 | |
|
|
1246 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1247 | except for idle watchers (which use the lock-out model). |
|
|
1248 | |
|
|
1249 | The rationale behind this is that implementing the lock-out model for |
|
|
1250 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1251 | libraries will just poll for the same events again and again as long as |
|
|
1252 | their callbacks have not been executed, which is very inefficient in the |
|
|
1253 | common case of one high-priority watcher locking out a mass of lower |
|
|
1254 | priority ones. |
|
|
1255 | |
|
|
1256 | Static (ordering) priorities are most useful when you have two or more |
|
|
1257 | watchers handling the same resource: a typical usage example is having an |
|
|
1258 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1259 | timeouts. Under load, data might be received while the program handles |
|
|
1260 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1261 | handler will be executed before checking for data. In that case, giving |
|
|
1262 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1263 | handled first even under adverse conditions (which is usually, but not |
|
|
1264 | always, what you want). |
|
|
1265 | |
|
|
1266 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1267 | will only be executed when no same or higher priority watchers have |
|
|
1268 | received events, they can be used to implement the "lock-out" model when |
|
|
1269 | required. |
|
|
1270 | |
|
|
1271 | For example, to emulate how many other event libraries handle priorities, |
|
|
1272 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1273 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1274 | processing is done in the idle watcher callback. This causes libev to |
|
|
1275 | continously poll and process kernel event data for the watcher, but when |
|
|
1276 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1277 | workable. |
|
|
1278 | |
|
|
1279 | Usually, however, the lock-out model implemented that way will perform |
|
|
1280 | miserably under the type of load it was designed to handle. In that case, |
|
|
1281 | it might be preferable to stop the real watcher before starting the |
|
|
1282 | idle watcher, so the kernel will not have to process the event in case |
|
|
1283 | the actual processing will be delayed for considerable time. |
|
|
1284 | |
|
|
1285 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1286 | priority than the default, and which should only process data when no |
|
|
1287 | other events are pending: |
|
|
1288 | |
|
|
1289 | ev_idle idle; // actual processing watcher |
|
|
1290 | ev_io io; // actual event watcher |
|
|
1291 | |
|
|
1292 | static void |
|
|
1293 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1294 | { |
|
|
1295 | // stop the I/O watcher, we received the event, but |
|
|
1296 | // are not yet ready to handle it. |
|
|
1297 | ev_io_stop (EV_A_ w); |
|
|
1298 | |
|
|
1299 | // start the idle watcher to ahndle the actual event. |
|
|
1300 | // it will not be executed as long as other watchers |
|
|
1301 | // with the default priority are receiving events. |
|
|
1302 | ev_idle_start (EV_A_ &idle); |
|
|
1303 | } |
|
|
1304 | |
|
|
1305 | static void |
|
|
1306 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1307 | { |
|
|
1308 | // actual processing |
|
|
1309 | read (STDIN_FILENO, ...); |
|
|
1310 | |
|
|
1311 | // have to start the I/O watcher again, as |
|
|
1312 | // we have handled the event |
|
|
1313 | ev_io_start (EV_P_ &io); |
|
|
1314 | } |
|
|
1315 | |
|
|
1316 | // initialisation |
|
|
1317 | ev_idle_init (&idle, idle_cb); |
|
|
1318 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1319 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1320 | |
|
|
1321 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1322 | low-priority connections can not be locked out forever under load. This |
|
|
1323 | enables your program to keep a lower latency for important connections |
|
|
1324 | during short periods of high load, while not completely locking out less |
|
|
1325 | important ones. |
960 | |
1326 | |
961 | |
1327 | |
962 | =head1 WATCHER TYPES |
1328 | =head1 WATCHER TYPES |
963 | |
1329 | |
964 | This section describes each watcher in detail, but will not repeat |
1330 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
988 | In general you can register as many read and/or write event watchers per |
1354 | In general you can register as many read and/or write event watchers per |
989 | fd as you want (as long as you don't confuse yourself). Setting all file |
1355 | fd as you want (as long as you don't confuse yourself). Setting all file |
990 | descriptors to non-blocking mode is also usually a good idea (but not |
1356 | descriptors to non-blocking mode is also usually a good idea (but not |
991 | required if you know what you are doing). |
1357 | required if you know what you are doing). |
992 | |
1358 | |
993 | If you must do this, then force the use of a known-to-be-good backend |
1359 | If you cannot use non-blocking mode, then force the use of a |
994 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1360 | known-to-be-good backend (at the time of this writing, this includes only |
995 | C<EVBACKEND_POLL>). |
1361 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1362 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1363 | files) - libev doesn't guarentee any specific behaviour in that case. |
996 | |
1364 | |
997 | Another thing you have to watch out for is that it is quite easy to |
1365 | Another thing you have to watch out for is that it is quite easy to |
998 | receive "spurious" readyness notifications, that is your callback might |
1366 | receive "spurious" readiness notifications, that is your callback might |
999 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1367 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1000 | because there is no data. Not only are some backends known to create a |
1368 | because there is no data. Not only are some backends known to create a |
1001 | lot of those (for example solaris ports), it is very easy to get into |
1369 | lot of those (for example Solaris ports), it is very easy to get into |
1002 | this situation even with a relatively standard program structure. Thus |
1370 | this situation even with a relatively standard program structure. Thus |
1003 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1371 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1004 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1372 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1005 | |
1373 | |
1006 | If you cannot run the fd in non-blocking mode (for example you should not |
1374 | If you cannot run the fd in non-blocking mode (for example you should |
1007 | play around with an Xlib connection), then you have to seperately re-test |
1375 | not play around with an Xlib connection), then you have to separately |
1008 | whether a file descriptor is really ready with a known-to-be good interface |
1376 | re-test whether a file descriptor is really ready with a known-to-be good |
1009 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1377 | interface such as poll (fortunately in our Xlib example, Xlib already |
1010 | its own, so its quite safe to use). |
1378 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1379 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1380 | indefinitely. |
|
|
1381 | |
|
|
1382 | But really, best use non-blocking mode. |
1011 | |
1383 | |
1012 | =head3 The special problem of disappearing file descriptors |
1384 | =head3 The special problem of disappearing file descriptors |
1013 | |
1385 | |
1014 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1386 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1015 | descriptor (either by calling C<close> explicitly or by any other means, |
1387 | descriptor (either due to calling C<close> explicitly or any other means, |
1016 | such as C<dup>). The reason is that you register interest in some file |
1388 | such as C<dup2>). The reason is that you register interest in some file |
1017 | descriptor, but when it goes away, the operating system will silently drop |
1389 | descriptor, but when it goes away, the operating system will silently drop |
1018 | this interest. If another file descriptor with the same number then is |
1390 | this interest. If another file descriptor with the same number then is |
1019 | registered with libev, there is no efficient way to see that this is, in |
1391 | registered with libev, there is no efficient way to see that this is, in |
1020 | fact, a different file descriptor. |
1392 | fact, a different file descriptor. |
1021 | |
1393 | |
… | |
… | |
1050 | To support fork in your programs, you either have to call |
1422 | To support fork in your programs, you either have to call |
1051 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1423 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1052 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1424 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1053 | C<EVBACKEND_POLL>. |
1425 | C<EVBACKEND_POLL>. |
1054 | |
1426 | |
|
|
1427 | =head3 The special problem of SIGPIPE |
|
|
1428 | |
|
|
1429 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
|
|
1430 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1431 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1432 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1433 | |
|
|
1434 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1435 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1436 | somewhere, as that would have given you a big clue). |
|
|
1437 | |
1055 | |
1438 | |
1056 | =head3 Watcher-Specific Functions |
1439 | =head3 Watcher-Specific Functions |
1057 | |
1440 | |
1058 | =over 4 |
1441 | =over 4 |
1059 | |
1442 | |
1060 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1443 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1061 | |
1444 | |
1062 | =item ev_io_set (ev_io *, int fd, int events) |
1445 | =item ev_io_set (ev_io *, int fd, int events) |
1063 | |
1446 | |
1064 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1447 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1065 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1448 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1066 | C<EV_READ | EV_WRITE> to receive the given events. |
1449 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1067 | |
1450 | |
1068 | =item int fd [read-only] |
1451 | =item int fd [read-only] |
1069 | |
1452 | |
1070 | The file descriptor being watched. |
1453 | The file descriptor being watched. |
1071 | |
1454 | |
… | |
… | |
1079 | |
1462 | |
1080 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1463 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1081 | readable, but only once. Since it is likely line-buffered, you could |
1464 | readable, but only once. Since it is likely line-buffered, you could |
1082 | attempt to read a whole line in the callback. |
1465 | attempt to read a whole line in the callback. |
1083 | |
1466 | |
1084 | static void |
1467 | static void |
1085 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1468 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1086 | { |
1469 | { |
1087 | ev_io_stop (loop, w); |
1470 | ev_io_stop (loop, w); |
1088 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1471 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1089 | } |
1472 | } |
1090 | |
1473 | |
1091 | ... |
1474 | ... |
1092 | struct ev_loop *loop = ev_default_init (0); |
1475 | struct ev_loop *loop = ev_default_init (0); |
1093 | struct ev_io stdin_readable; |
1476 | ev_io stdin_readable; |
1094 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1477 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1095 | ev_io_start (loop, &stdin_readable); |
1478 | ev_io_start (loop, &stdin_readable); |
1096 | ev_loop (loop, 0); |
1479 | ev_loop (loop, 0); |
1097 | |
1480 | |
1098 | |
1481 | |
1099 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1482 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1100 | |
1483 | |
1101 | Timer watchers are simple relative timers that generate an event after a |
1484 | Timer watchers are simple relative timers that generate an event after a |
1102 | given time, and optionally repeating in regular intervals after that. |
1485 | given time, and optionally repeating in regular intervals after that. |
1103 | |
1486 | |
1104 | The timers are based on real time, that is, if you register an event that |
1487 | The timers are based on real time, that is, if you register an event that |
1105 | times out after an hour and you reset your system clock to last years |
1488 | times out after an hour and you reset your system clock to January last |
1106 | time, it will still time out after (roughly) and hour. "Roughly" because |
1489 | year, it will still time out after (roughly) one hour. "Roughly" because |
1107 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1490 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1108 | monotonic clock option helps a lot here). |
1491 | monotonic clock option helps a lot here). |
|
|
1492 | |
|
|
1493 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1494 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1495 | might introduce a small delay). If multiple timers become ready during the |
|
|
1496 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1497 | before ones of the same priority with later time-out values (but this is |
|
|
1498 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1499 | |
|
|
1500 | =head3 Be smart about timeouts |
|
|
1501 | |
|
|
1502 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1503 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1504 | you want to raise some error after a while. |
|
|
1505 | |
|
|
1506 | What follows are some ways to handle this problem, from obvious and |
|
|
1507 | inefficient to smart and efficient. |
|
|
1508 | |
|
|
1509 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1510 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1511 | data or other life sign was received). |
|
|
1512 | |
|
|
1513 | =over 4 |
|
|
1514 | |
|
|
1515 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1516 | |
|
|
1517 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1518 | start the watcher: |
|
|
1519 | |
|
|
1520 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1521 | ev_timer_start (loop, timer); |
|
|
1522 | |
|
|
1523 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1524 | and start it again: |
|
|
1525 | |
|
|
1526 | ev_timer_stop (loop, timer); |
|
|
1527 | ev_timer_set (timer, 60., 0.); |
|
|
1528 | ev_timer_start (loop, timer); |
|
|
1529 | |
|
|
1530 | This is relatively simple to implement, but means that each time there is |
|
|
1531 | some activity, libev will first have to remove the timer from its internal |
|
|
1532 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1533 | still not a constant-time operation. |
|
|
1534 | |
|
|
1535 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1536 | |
|
|
1537 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1538 | C<ev_timer_start>. |
|
|
1539 | |
|
|
1540 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1541 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1542 | successfully read or write some data. If you go into an idle state where |
|
|
1543 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1544 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1545 | |
|
|
1546 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1547 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1548 | member and C<ev_timer_again>. |
|
|
1549 | |
|
|
1550 | At start: |
|
|
1551 | |
|
|
1552 | ev_init (timer, callback); |
|
|
1553 | timer->repeat = 60.; |
|
|
1554 | ev_timer_again (loop, timer); |
|
|
1555 | |
|
|
1556 | Each time there is some activity: |
|
|
1557 | |
|
|
1558 | ev_timer_again (loop, timer); |
|
|
1559 | |
|
|
1560 | It is even possible to change the time-out on the fly, regardless of |
|
|
1561 | whether the watcher is active or not: |
|
|
1562 | |
|
|
1563 | timer->repeat = 30.; |
|
|
1564 | ev_timer_again (loop, timer); |
|
|
1565 | |
|
|
1566 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1567 | you want to modify its timeout value, as libev does not have to completely |
|
|
1568 | remove and re-insert the timer from/into its internal data structure. |
|
|
1569 | |
|
|
1570 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1571 | |
|
|
1572 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1573 | |
|
|
1574 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1575 | relatively long compared to the intervals between other activity - in |
|
|
1576 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1577 | associated activity resets. |
|
|
1578 | |
|
|
1579 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1580 | but remember the time of last activity, and check for a real timeout only |
|
|
1581 | within the callback: |
|
|
1582 | |
|
|
1583 | ev_tstamp last_activity; // time of last activity |
|
|
1584 | |
|
|
1585 | static void |
|
|
1586 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1587 | { |
|
|
1588 | ev_tstamp now = ev_now (EV_A); |
|
|
1589 | ev_tstamp timeout = last_activity + 60.; |
|
|
1590 | |
|
|
1591 | // if last_activity + 60. is older than now, we did time out |
|
|
1592 | if (timeout < now) |
|
|
1593 | { |
|
|
1594 | // timeout occured, take action |
|
|
1595 | } |
|
|
1596 | else |
|
|
1597 | { |
|
|
1598 | // callback was invoked, but there was some activity, re-arm |
|
|
1599 | // the watcher to fire in last_activity + 60, which is |
|
|
1600 | // guaranteed to be in the future, so "again" is positive: |
|
|
1601 | w->repeat = timeout - now; |
|
|
1602 | ev_timer_again (EV_A_ w); |
|
|
1603 | } |
|
|
1604 | } |
|
|
1605 | |
|
|
1606 | To summarise the callback: first calculate the real timeout (defined |
|
|
1607 | as "60 seconds after the last activity"), then check if that time has |
|
|
1608 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1609 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1610 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1611 | a timeout then. |
|
|
1612 | |
|
|
1613 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1614 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1615 | |
|
|
1616 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1617 | minus half the average time between activity), but virtually no calls to |
|
|
1618 | libev to change the timeout. |
|
|
1619 | |
|
|
1620 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1621 | to the current time (meaning we just have some activity :), then call the |
|
|
1622 | callback, which will "do the right thing" and start the timer: |
|
|
1623 | |
|
|
1624 | ev_init (timer, callback); |
|
|
1625 | last_activity = ev_now (loop); |
|
|
1626 | callback (loop, timer, EV_TIMEOUT); |
|
|
1627 | |
|
|
1628 | And when there is some activity, simply store the current time in |
|
|
1629 | C<last_activity>, no libev calls at all: |
|
|
1630 | |
|
|
1631 | last_actiivty = ev_now (loop); |
|
|
1632 | |
|
|
1633 | This technique is slightly more complex, but in most cases where the |
|
|
1634 | time-out is unlikely to be triggered, much more efficient. |
|
|
1635 | |
|
|
1636 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1637 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1638 | fix things for you. |
|
|
1639 | |
|
|
1640 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1641 | |
|
|
1642 | If there is not one request, but many thousands (millions...), all |
|
|
1643 | employing some kind of timeout with the same timeout value, then one can |
|
|
1644 | do even better: |
|
|
1645 | |
|
|
1646 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1647 | at the I<end> of the list. |
|
|
1648 | |
|
|
1649 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1650 | the list is expected to fire (for example, using the technique #3). |
|
|
1651 | |
|
|
1652 | When there is some activity, remove the timer from the list, recalculate |
|
|
1653 | the timeout, append it to the end of the list again, and make sure to |
|
|
1654 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1655 | |
|
|
1656 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1657 | starting, stopping and updating the timers, at the expense of a major |
|
|
1658 | complication, and having to use a constant timeout. The constant timeout |
|
|
1659 | ensures that the list stays sorted. |
|
|
1660 | |
|
|
1661 | =back |
|
|
1662 | |
|
|
1663 | So which method the best? |
|
|
1664 | |
|
|
1665 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1666 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1667 | better, and isn't very complicated either. In most case, choosing either |
|
|
1668 | one is fine, with #3 being better in typical situations. |
|
|
1669 | |
|
|
1670 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1671 | rather complicated, but extremely efficient, something that really pays |
|
|
1672 | off after the first million or so of active timers, i.e. it's usually |
|
|
1673 | overkill :) |
|
|
1674 | |
|
|
1675 | =head3 The special problem of time updates |
|
|
1676 | |
|
|
1677 | Establishing the current time is a costly operation (it usually takes at |
|
|
1678 | least two system calls): EV therefore updates its idea of the current |
|
|
1679 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1680 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1681 | lots of events in one iteration. |
1109 | |
1682 | |
1110 | The relative timeouts are calculated relative to the C<ev_now ()> |
1683 | The relative timeouts are calculated relative to the C<ev_now ()> |
1111 | time. This is usually the right thing as this timestamp refers to the time |
1684 | time. This is usually the right thing as this timestamp refers to the time |
1112 | of the event triggering whatever timeout you are modifying/starting. If |
1685 | of the event triggering whatever timeout you are modifying/starting. If |
1113 | you suspect event processing to be delayed and you I<need> to base the timeout |
1686 | you suspect event processing to be delayed and you I<need> to base the |
1114 | on the current time, use something like this to adjust for this: |
1687 | timeout on the current time, use something like this to adjust for this: |
1115 | |
1688 | |
1116 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1689 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1117 | |
1690 | |
1118 | The callback is guarenteed to be invoked only when its timeout has passed, |
1691 | If the event loop is suspended for a long time, you can also force an |
1119 | but if multiple timers become ready during the same loop iteration then |
1692 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1120 | order of execution is undefined. |
1693 | ()>. |
1121 | |
1694 | |
1122 | =head3 Watcher-Specific Functions and Data Members |
1695 | =head3 Watcher-Specific Functions and Data Members |
1123 | |
1696 | |
1124 | =over 4 |
1697 | =over 4 |
1125 | |
1698 | |
1126 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1699 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1127 | |
1700 | |
1128 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1701 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1129 | |
1702 | |
1130 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1703 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1131 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1704 | is C<0.>, then it will automatically be stopped once the timeout is |
1132 | timer will automatically be configured to trigger again C<repeat> seconds |
1705 | reached. If it is positive, then the timer will automatically be |
1133 | later, again, and again, until stopped manually. |
1706 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1707 | until stopped manually. |
1134 | |
1708 | |
1135 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1709 | The timer itself will do a best-effort at avoiding drift, that is, if |
1136 | configure a timer to trigger every 10 seconds, then it will trigger at |
1710 | you configure a timer to trigger every 10 seconds, then it will normally |
1137 | exactly 10 second intervals. If, however, your program cannot keep up with |
1711 | trigger at exactly 10 second intervals. If, however, your program cannot |
1138 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1712 | keep up with the timer (because it takes longer than those 10 seconds to |
1139 | timer will not fire more than once per event loop iteration. |
1713 | do stuff) the timer will not fire more than once per event loop iteration. |
1140 | |
1714 | |
1141 | =item ev_timer_again (loop) |
1715 | =item ev_timer_again (loop, ev_timer *) |
1142 | |
1716 | |
1143 | This will act as if the timer timed out and restart it again if it is |
1717 | This will act as if the timer timed out and restart it again if it is |
1144 | repeating. The exact semantics are: |
1718 | repeating. The exact semantics are: |
1145 | |
1719 | |
1146 | If the timer is pending, its pending status is cleared. |
1720 | If the timer is pending, its pending status is cleared. |
1147 | |
1721 | |
1148 | If the timer is started but nonrepeating, stop it (as if it timed out). |
1722 | If the timer is started but non-repeating, stop it (as if it timed out). |
1149 | |
1723 | |
1150 | If the timer is repeating, either start it if necessary (with the |
1724 | If the timer is repeating, either start it if necessary (with the |
1151 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1725 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1152 | |
1726 | |
1153 | This sounds a bit complicated, but here is a useful and typical |
1727 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1154 | example: Imagine you have a tcp connection and you want a so-called idle |
1728 | usage example. |
1155 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1156 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1157 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1158 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1159 | you go into an idle state where you do not expect data to travel on the |
|
|
1160 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1161 | automatically restart it if need be. |
|
|
1162 | |
|
|
1163 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1164 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1165 | |
|
|
1166 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1167 | ev_timer_again (loop, timer); |
|
|
1168 | ... |
|
|
1169 | timer->again = 17.; |
|
|
1170 | ev_timer_again (loop, timer); |
|
|
1171 | ... |
|
|
1172 | timer->again = 10.; |
|
|
1173 | ev_timer_again (loop, timer); |
|
|
1174 | |
|
|
1175 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1176 | you want to modify its timeout value. |
|
|
1177 | |
1729 | |
1178 | =item ev_tstamp repeat [read-write] |
1730 | =item ev_tstamp repeat [read-write] |
1179 | |
1731 | |
1180 | The current C<repeat> value. Will be used each time the watcher times out |
1732 | The current C<repeat> value. Will be used each time the watcher times out |
1181 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1733 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1182 | which is also when any modifications are taken into account. |
1734 | which is also when any modifications are taken into account. |
1183 | |
1735 | |
1184 | =back |
1736 | =back |
1185 | |
1737 | |
1186 | =head3 Examples |
1738 | =head3 Examples |
1187 | |
1739 | |
1188 | Example: Create a timer that fires after 60 seconds. |
1740 | Example: Create a timer that fires after 60 seconds. |
1189 | |
1741 | |
1190 | static void |
1742 | static void |
1191 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1743 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1192 | { |
1744 | { |
1193 | .. one minute over, w is actually stopped right here |
1745 | .. one minute over, w is actually stopped right here |
1194 | } |
1746 | } |
1195 | |
1747 | |
1196 | struct ev_timer mytimer; |
1748 | ev_timer mytimer; |
1197 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1749 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1198 | ev_timer_start (loop, &mytimer); |
1750 | ev_timer_start (loop, &mytimer); |
1199 | |
1751 | |
1200 | Example: Create a timeout timer that times out after 10 seconds of |
1752 | Example: Create a timeout timer that times out after 10 seconds of |
1201 | inactivity. |
1753 | inactivity. |
1202 | |
1754 | |
1203 | static void |
1755 | static void |
1204 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1756 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1205 | { |
1757 | { |
1206 | .. ten seconds without any activity |
1758 | .. ten seconds without any activity |
1207 | } |
1759 | } |
1208 | |
1760 | |
1209 | struct ev_timer mytimer; |
1761 | ev_timer mytimer; |
1210 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1762 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1211 | ev_timer_again (&mytimer); /* start timer */ |
1763 | ev_timer_again (&mytimer); /* start timer */ |
1212 | ev_loop (loop, 0); |
1764 | ev_loop (loop, 0); |
1213 | |
1765 | |
1214 | // and in some piece of code that gets executed on any "activity": |
1766 | // and in some piece of code that gets executed on any "activity": |
1215 | // reset the timeout to start ticking again at 10 seconds |
1767 | // reset the timeout to start ticking again at 10 seconds |
1216 | ev_timer_again (&mytimer); |
1768 | ev_timer_again (&mytimer); |
1217 | |
1769 | |
1218 | |
1770 | |
1219 | =head2 C<ev_periodic> - to cron or not to cron? |
1771 | =head2 C<ev_periodic> - to cron or not to cron? |
1220 | |
1772 | |
1221 | Periodic watchers are also timers of a kind, but they are very versatile |
1773 | Periodic watchers are also timers of a kind, but they are very versatile |
1222 | (and unfortunately a bit complex). |
1774 | (and unfortunately a bit complex). |
1223 | |
1775 | |
1224 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1776 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1225 | but on wallclock time (absolute time). You can tell a periodic watcher |
1777 | relative time, the physical time that passes) but on wall clock time |
1226 | to trigger "at" some specific point in time. For example, if you tell a |
1778 | (absolute time, the thing you can read on your calender or clock). The |
1227 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1779 | difference is that wall clock time can run faster or slower than real |
1228 | + 10.>) and then reset your system clock to the last year, then it will |
1780 | time, and time jumps are not uncommon (e.g. when you adjust your |
1229 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1781 | wrist-watch). |
1230 | roughly 10 seconds later). |
|
|
1231 | |
1782 | |
1232 | They can also be used to implement vastly more complex timers, such as |
1783 | You can tell a periodic watcher to trigger after some specific point |
1233 | triggering an event on each midnight, local time or other, complicated, |
1784 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
1234 | rules. |
1785 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1786 | not a delay) and then reset your system clock to January of the previous |
|
|
1787 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1788 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1789 | it, as it uses a relative timeout). |
1235 | |
1790 | |
|
|
1791 | C<ev_periodic> watchers can also be used to implement vastly more complex |
|
|
1792 | timers, such as triggering an event on each "midnight, local time", or |
|
|
1793 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1794 | those cannot react to time jumps. |
|
|
1795 | |
1236 | As with timers, the callback is guarenteed to be invoked only when the |
1796 | As with timers, the callback is guaranteed to be invoked only when the |
1237 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1797 | point in time where it is supposed to trigger has passed. If multiple |
1238 | during the same loop iteration then order of execution is undefined. |
1798 | timers become ready during the same loop iteration then the ones with |
|
|
1799 | earlier time-out values are invoked before ones with later time-out values |
|
|
1800 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1239 | |
1801 | |
1240 | =head3 Watcher-Specific Functions and Data Members |
1802 | =head3 Watcher-Specific Functions and Data Members |
1241 | |
1803 | |
1242 | =over 4 |
1804 | =over 4 |
1243 | |
1805 | |
1244 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1806 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1245 | |
1807 | |
1246 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1808 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1247 | |
1809 | |
1248 | Lots of arguments, lets sort it out... There are basically three modes of |
1810 | Lots of arguments, let's sort it out... There are basically three modes of |
1249 | operation, and we will explain them from simplest to complex: |
1811 | operation, and we will explain them from simplest to most complex: |
1250 | |
1812 | |
1251 | =over 4 |
1813 | =over 4 |
1252 | |
1814 | |
1253 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1815 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1254 | |
1816 | |
1255 | In this configuration the watcher triggers an event at the wallclock time |
1817 | In this configuration the watcher triggers an event after the wall clock |
1256 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1818 | time C<offset> has passed. It will not repeat and will not adjust when a |
1257 | that is, if it is to be run at January 1st 2011 then it will run when the |
1819 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1258 | system time reaches or surpasses this time. |
1820 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1821 | this point in time. |
1259 | |
1822 | |
1260 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1823 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1261 | |
1824 | |
1262 | In this mode the watcher will always be scheduled to time out at the next |
1825 | In this mode the watcher will always be scheduled to time out at the next |
1263 | C<at + N * interval> time (for some integer N, which can also be negative) |
1826 | C<offset + N * interval> time (for some integer N, which can also be |
1264 | and then repeat, regardless of any time jumps. |
1827 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1828 | argument is merely an offset into the C<interval> periods. |
1265 | |
1829 | |
1266 | This can be used to create timers that do not drift with respect to system |
1830 | This can be used to create timers that do not drift with respect to the |
1267 | time: |
1831 | system clock, for example, here is an C<ev_periodic> that triggers each |
|
|
1832 | hour, on the hour (with respect to UTC): |
1268 | |
1833 | |
1269 | ev_periodic_set (&periodic, 0., 3600., 0); |
1834 | ev_periodic_set (&periodic, 0., 3600., 0); |
1270 | |
1835 | |
1271 | This doesn't mean there will always be 3600 seconds in between triggers, |
1836 | This doesn't mean there will always be 3600 seconds in between triggers, |
1272 | but only that the the callback will be called when the system time shows a |
1837 | but only that the callback will be called when the system time shows a |
1273 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1838 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1274 | by 3600. |
1839 | by 3600. |
1275 | |
1840 | |
1276 | Another way to think about it (for the mathematically inclined) is that |
1841 | Another way to think about it (for the mathematically inclined) is that |
1277 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1842 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1278 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1843 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1279 | |
1844 | |
1280 | For numerical stability it is preferable that the C<at> value is near |
1845 | For numerical stability it is preferable that the C<offset> value is near |
1281 | C<ev_now ()> (the current time), but there is no range requirement for |
1846 | C<ev_now ()> (the current time), but there is no range requirement for |
1282 | this value. |
1847 | this value, and in fact is often specified as zero. |
1283 | |
1848 | |
|
|
1849 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1850 | speed for example), so if C<interval> is very small then timing stability |
|
|
1851 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1852 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1853 | |
1284 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1854 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1285 | |
1855 | |
1286 | In this mode the values for C<interval> and C<at> are both being |
1856 | In this mode the values for C<interval> and C<offset> are both being |
1287 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1857 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1288 | reschedule callback will be called with the watcher as first, and the |
1858 | reschedule callback will be called with the watcher as first, and the |
1289 | current time as second argument. |
1859 | current time as second argument. |
1290 | |
1860 | |
1291 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1861 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1292 | ever, or make any event loop modifications>. If you need to stop it, |
1862 | or make ANY other event loop modifications whatsoever, unless explicitly |
1293 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1863 | allowed by documentation here>. |
1294 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1295 | |
1864 | |
|
|
1865 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1866 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1867 | only event loop modification you are allowed to do). |
|
|
1868 | |
1296 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1869 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1297 | ev_tstamp now)>, e.g.: |
1870 | *w, ev_tstamp now)>, e.g.: |
1298 | |
1871 | |
|
|
1872 | static ev_tstamp |
1299 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1873 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1300 | { |
1874 | { |
1301 | return now + 60.; |
1875 | return now + 60.; |
1302 | } |
1876 | } |
1303 | |
1877 | |
1304 | It must return the next time to trigger, based on the passed time value |
1878 | It must return the next time to trigger, based on the passed time value |
1305 | (that is, the lowest time value larger than to the second argument). It |
1879 | (that is, the lowest time value larger than to the second argument). It |
1306 | will usually be called just before the callback will be triggered, but |
1880 | will usually be called just before the callback will be triggered, but |
1307 | might be called at other times, too. |
1881 | might be called at other times, too. |
1308 | |
1882 | |
1309 | NOTE: I<< This callback must always return a time that is later than the |
1883 | NOTE: I<< This callback must always return a time that is higher than or |
1310 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1884 | equal to the passed C<now> value >>. |
1311 | |
1885 | |
1312 | This can be used to create very complex timers, such as a timer that |
1886 | This can be used to create very complex timers, such as a timer that |
1313 | triggers on each midnight, local time. To do this, you would calculate the |
1887 | triggers on "next midnight, local time". To do this, you would calculate the |
1314 | next midnight after C<now> and return the timestamp value for this. How |
1888 | next midnight after C<now> and return the timestamp value for this. How |
1315 | you do this is, again, up to you (but it is not trivial, which is the main |
1889 | you do this is, again, up to you (but it is not trivial, which is the main |
1316 | reason I omitted it as an example). |
1890 | reason I omitted it as an example). |
1317 | |
1891 | |
1318 | =back |
1892 | =back |
… | |
… | |
1322 | Simply stops and restarts the periodic watcher again. This is only useful |
1896 | Simply stops and restarts the periodic watcher again. This is only useful |
1323 | when you changed some parameters or the reschedule callback would return |
1897 | when you changed some parameters or the reschedule callback would return |
1324 | a different time than the last time it was called (e.g. in a crond like |
1898 | a different time than the last time it was called (e.g. in a crond like |
1325 | program when the crontabs have changed). |
1899 | program when the crontabs have changed). |
1326 | |
1900 | |
|
|
1901 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1902 | |
|
|
1903 | When active, returns the absolute time that the watcher is supposed |
|
|
1904 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1905 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1906 | rescheduling modes. |
|
|
1907 | |
1327 | =item ev_tstamp offset [read-write] |
1908 | =item ev_tstamp offset [read-write] |
1328 | |
1909 | |
1329 | When repeating, this contains the offset value, otherwise this is the |
1910 | When repeating, this contains the offset value, otherwise this is the |
1330 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1911 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1912 | although libev might modify this value for better numerical stability). |
1331 | |
1913 | |
1332 | Can be modified any time, but changes only take effect when the periodic |
1914 | Can be modified any time, but changes only take effect when the periodic |
1333 | timer fires or C<ev_periodic_again> is being called. |
1915 | timer fires or C<ev_periodic_again> is being called. |
1334 | |
1916 | |
1335 | =item ev_tstamp interval [read-write] |
1917 | =item ev_tstamp interval [read-write] |
1336 | |
1918 | |
1337 | The current interval value. Can be modified any time, but changes only |
1919 | The current interval value. Can be modified any time, but changes only |
1338 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1920 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1339 | called. |
1921 | called. |
1340 | |
1922 | |
1341 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1923 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1342 | |
1924 | |
1343 | The current reschedule callback, or C<0>, if this functionality is |
1925 | The current reschedule callback, or C<0>, if this functionality is |
1344 | switched off. Can be changed any time, but changes only take effect when |
1926 | switched off. Can be changed any time, but changes only take effect when |
1345 | the periodic timer fires or C<ev_periodic_again> is being called. |
1927 | the periodic timer fires or C<ev_periodic_again> is being called. |
1346 | |
1928 | |
1347 | =item ev_tstamp at [read-only] |
|
|
1348 | |
|
|
1349 | When active, contains the absolute time that the watcher is supposed to |
|
|
1350 | trigger next. |
|
|
1351 | |
|
|
1352 | =back |
1929 | =back |
1353 | |
1930 | |
1354 | =head3 Examples |
1931 | =head3 Examples |
1355 | |
1932 | |
1356 | Example: Call a callback every hour, or, more precisely, whenever the |
1933 | Example: Call a callback every hour, or, more precisely, whenever the |
1357 | system clock is divisible by 3600. The callback invocation times have |
1934 | system time is divisible by 3600. The callback invocation times have |
1358 | potentially a lot of jittering, but good long-term stability. |
1935 | potentially a lot of jitter, but good long-term stability. |
1359 | |
1936 | |
1360 | static void |
1937 | static void |
1361 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1938 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1362 | { |
1939 | { |
1363 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1940 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1364 | } |
1941 | } |
1365 | |
1942 | |
1366 | struct ev_periodic hourly_tick; |
1943 | ev_periodic hourly_tick; |
1367 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1944 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1368 | ev_periodic_start (loop, &hourly_tick); |
1945 | ev_periodic_start (loop, &hourly_tick); |
1369 | |
1946 | |
1370 | Example: The same as above, but use a reschedule callback to do it: |
1947 | Example: The same as above, but use a reschedule callback to do it: |
1371 | |
1948 | |
1372 | #include <math.h> |
1949 | #include <math.h> |
1373 | |
1950 | |
1374 | static ev_tstamp |
1951 | static ev_tstamp |
1375 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1952 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1376 | { |
1953 | { |
1377 | return fmod (now, 3600.) + 3600.; |
1954 | return now + (3600. - fmod (now, 3600.)); |
1378 | } |
1955 | } |
1379 | |
1956 | |
1380 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1957 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1381 | |
1958 | |
1382 | Example: Call a callback every hour, starting now: |
1959 | Example: Call a callback every hour, starting now: |
1383 | |
1960 | |
1384 | struct ev_periodic hourly_tick; |
1961 | ev_periodic hourly_tick; |
1385 | ev_periodic_init (&hourly_tick, clock_cb, |
1962 | ev_periodic_init (&hourly_tick, clock_cb, |
1386 | fmod (ev_now (loop), 3600.), 3600., 0); |
1963 | fmod (ev_now (loop), 3600.), 3600., 0); |
1387 | ev_periodic_start (loop, &hourly_tick); |
1964 | ev_periodic_start (loop, &hourly_tick); |
1388 | |
1965 | |
1389 | |
1966 | |
1390 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1967 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1391 | |
1968 | |
1392 | Signal watchers will trigger an event when the process receives a specific |
1969 | Signal watchers will trigger an event when the process receives a specific |
1393 | signal one or more times. Even though signals are very asynchronous, libev |
1970 | signal one or more times. Even though signals are very asynchronous, libev |
1394 | will try it's best to deliver signals synchronously, i.e. as part of the |
1971 | will try it's best to deliver signals synchronously, i.e. as part of the |
1395 | normal event processing, like any other event. |
1972 | normal event processing, like any other event. |
1396 | |
1973 | |
|
|
1974 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1975 | do without libev and forget about sharing the signal. You can even use |
|
|
1976 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1977 | |
1397 | You can configure as many watchers as you like per signal. Only when the |
1978 | You can configure as many watchers as you like per signal. Only when the |
1398 | first watcher gets started will libev actually register a signal watcher |
1979 | first watcher gets started will libev actually register a signal handler |
1399 | with the kernel (thus it coexists with your own signal handlers as long |
1980 | with the kernel (thus it coexists with your own signal handlers as long as |
1400 | as you don't register any with libev). Similarly, when the last signal |
1981 | you don't register any with libev for the same signal). Similarly, when |
1401 | watcher for a signal is stopped libev will reset the signal handler to |
1982 | the last signal watcher for a signal is stopped, libev will reset the |
1402 | SIG_DFL (regardless of what it was set to before). |
1983 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1984 | |
|
|
1985 | If possible and supported, libev will install its handlers with |
|
|
1986 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1987 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1988 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1989 | them in an C<ev_prepare> watcher. |
1403 | |
1990 | |
1404 | =head3 Watcher-Specific Functions and Data Members |
1991 | =head3 Watcher-Specific Functions and Data Members |
1405 | |
1992 | |
1406 | =over 4 |
1993 | =over 4 |
1407 | |
1994 | |
… | |
… | |
1416 | |
2003 | |
1417 | The signal the watcher watches out for. |
2004 | The signal the watcher watches out for. |
1418 | |
2005 | |
1419 | =back |
2006 | =back |
1420 | |
2007 | |
|
|
2008 | =head3 Examples |
|
|
2009 | |
|
|
2010 | Example: Try to exit cleanly on SIGINT. |
|
|
2011 | |
|
|
2012 | static void |
|
|
2013 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
2014 | { |
|
|
2015 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
2016 | } |
|
|
2017 | |
|
|
2018 | ev_signal signal_watcher; |
|
|
2019 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
2020 | ev_signal_start (loop, &signal_watcher); |
|
|
2021 | |
1421 | |
2022 | |
1422 | =head2 C<ev_child> - watch out for process status changes |
2023 | =head2 C<ev_child> - watch out for process status changes |
1423 | |
2024 | |
1424 | Child watchers trigger when your process receives a SIGCHLD in response to |
2025 | Child watchers trigger when your process receives a SIGCHLD in response to |
1425 | some child status changes (most typically when a child of yours dies). |
2026 | some child status changes (most typically when a child of yours dies or |
|
|
2027 | exits). It is permissible to install a child watcher I<after> the child |
|
|
2028 | has been forked (which implies it might have already exited), as long |
|
|
2029 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2030 | forking and then immediately registering a watcher for the child is fine, |
|
|
2031 | but forking and registering a watcher a few event loop iterations later or |
|
|
2032 | in the next callback invocation is not. |
|
|
2033 | |
|
|
2034 | Only the default event loop is capable of handling signals, and therefore |
|
|
2035 | you can only register child watchers in the default event loop. |
|
|
2036 | |
|
|
2037 | Due to some design glitches inside libev, child watchers will always be |
|
|
2038 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2039 | libev) |
|
|
2040 | |
|
|
2041 | =head3 Process Interaction |
|
|
2042 | |
|
|
2043 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
2044 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
2045 | the first child watcher is started after the child exits. The occurrence |
|
|
2046 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
2047 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
2048 | children, even ones not watched. |
|
|
2049 | |
|
|
2050 | =head3 Overriding the Built-In Processing |
|
|
2051 | |
|
|
2052 | Libev offers no special support for overriding the built-in child |
|
|
2053 | processing, but if your application collides with libev's default child |
|
|
2054 | handler, you can override it easily by installing your own handler for |
|
|
2055 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
2056 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
2057 | event-based approach to child reaping and thus use libev's support for |
|
|
2058 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2059 | |
|
|
2060 | =head3 Stopping the Child Watcher |
|
|
2061 | |
|
|
2062 | Currently, the child watcher never gets stopped, even when the |
|
|
2063 | child terminates, so normally one needs to stop the watcher in the |
|
|
2064 | callback. Future versions of libev might stop the watcher automatically |
|
|
2065 | when a child exit is detected. |
1426 | |
2066 | |
1427 | =head3 Watcher-Specific Functions and Data Members |
2067 | =head3 Watcher-Specific Functions and Data Members |
1428 | |
2068 | |
1429 | =over 4 |
2069 | =over 4 |
1430 | |
2070 | |
1431 | =item ev_child_init (ev_child *, callback, int pid) |
2071 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
1432 | |
2072 | |
1433 | =item ev_child_set (ev_child *, int pid) |
2073 | =item ev_child_set (ev_child *, int pid, int trace) |
1434 | |
2074 | |
1435 | Configures the watcher to wait for status changes of process C<pid> (or |
2075 | Configures the watcher to wait for status changes of process C<pid> (or |
1436 | I<any> process if C<pid> is specified as C<0>). The callback can look |
2076 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1437 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
2077 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1438 | the status word (use the macros from C<sys/wait.h> and see your systems |
2078 | the status word (use the macros from C<sys/wait.h> and see your systems |
1439 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
2079 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1440 | process causing the status change. |
2080 | process causing the status change. C<trace> must be either C<0> (only |
|
|
2081 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
2082 | activate the watcher when the process is stopped or continued). |
1441 | |
2083 | |
1442 | =item int pid [read-only] |
2084 | =item int pid [read-only] |
1443 | |
2085 | |
1444 | The process id this watcher watches out for, or C<0>, meaning any process id. |
2086 | The process id this watcher watches out for, or C<0>, meaning any process id. |
1445 | |
2087 | |
… | |
… | |
1454 | |
2096 | |
1455 | =back |
2097 | =back |
1456 | |
2098 | |
1457 | =head3 Examples |
2099 | =head3 Examples |
1458 | |
2100 | |
1459 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2101 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
2102 | its completion. |
1460 | |
2103 | |
|
|
2104 | ev_child cw; |
|
|
2105 | |
1461 | static void |
2106 | static void |
1462 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2107 | child_cb (EV_P_ ev_child *w, int revents) |
1463 | { |
2108 | { |
1464 | ev_unloop (loop, EVUNLOOP_ALL); |
2109 | ev_child_stop (EV_A_ w); |
|
|
2110 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1465 | } |
2111 | } |
1466 | |
2112 | |
1467 | struct ev_signal signal_watcher; |
2113 | pid_t pid = fork (); |
1468 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2114 | |
1469 | ev_signal_start (loop, &sigint_cb); |
2115 | if (pid < 0) |
|
|
2116 | // error |
|
|
2117 | else if (pid == 0) |
|
|
2118 | { |
|
|
2119 | // the forked child executes here |
|
|
2120 | exit (1); |
|
|
2121 | } |
|
|
2122 | else |
|
|
2123 | { |
|
|
2124 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
2125 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
2126 | } |
1470 | |
2127 | |
1471 | |
2128 | |
1472 | =head2 C<ev_stat> - did the file attributes just change? |
2129 | =head2 C<ev_stat> - did the file attributes just change? |
1473 | |
2130 | |
1474 | This watches a filesystem path for attribute changes. That is, it calls |
2131 | This watches a file system path for attribute changes. That is, it calls |
1475 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2132 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1476 | compared to the last time, invoking the callback if it did. |
2133 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2134 | it did. |
1477 | |
2135 | |
1478 | The path does not need to exist: changing from "path exists" to "path does |
2136 | The path does not need to exist: changing from "path exists" to "path does |
1479 | not exist" is a status change like any other. The condition "path does |
2137 | not exist" is a status change like any other. The condition "path does not |
1480 | not exist" is signified by the C<st_nlink> field being zero (which is |
2138 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1481 | otherwise always forced to be at least one) and all the other fields of |
2139 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1482 | the stat buffer having unspecified contents. |
2140 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2141 | contents. |
1483 | |
2142 | |
1484 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2143 | The path I<must not> end in a slash or contain special components such as |
|
|
2144 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1485 | relative and your working directory changes, the behaviour is undefined. |
2145 | your working directory changes, then the behaviour is undefined. |
1486 | |
2146 | |
1487 | Since there is no standard to do this, the portable implementation simply |
2147 | Since there is no portable change notification interface available, the |
1488 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2148 | portable implementation simply calls C<stat(2)> regularly on the path |
1489 | can specify a recommended polling interval for this case. If you specify |
2149 | to see if it changed somehow. You can specify a recommended polling |
1490 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2150 | interval for this case. If you specify a polling interval of C<0> (highly |
1491 | unspecified default> value will be used (which you can expect to be around |
2151 | recommended!) then a I<suitable, unspecified default> value will be used |
1492 | five seconds, although this might change dynamically). Libev will also |
2152 | (which you can expect to be around five seconds, although this might |
1493 | impose a minimum interval which is currently around C<0.1>, but thats |
2153 | change dynamically). Libev will also impose a minimum interval which is |
1494 | usually overkill. |
2154 | currently around C<0.1>, but that's usually overkill. |
1495 | |
2155 | |
1496 | This watcher type is not meant for massive numbers of stat watchers, |
2156 | This watcher type is not meant for massive numbers of stat watchers, |
1497 | as even with OS-supported change notifications, this can be |
2157 | as even with OS-supported change notifications, this can be |
1498 | resource-intensive. |
2158 | resource-intensive. |
1499 | |
2159 | |
1500 | At the time of this writing, only the Linux inotify interface is |
2160 | At the time of this writing, the only OS-specific interface implemented |
1501 | implemented (implementing kqueue support is left as an exercise for the |
2161 | is the Linux inotify interface (implementing kqueue support is left as an |
1502 | reader). Inotify will be used to give hints only and should not change the |
2162 | exercise for the reader. Note, however, that the author sees no way of |
1503 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
2163 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1504 | to fall back to regular polling again even with inotify, but changes are |
|
|
1505 | usually detected immediately, and if the file exists there will be no |
|
|
1506 | polling. |
|
|
1507 | |
2164 | |
1508 | =head3 Inotify |
2165 | =head3 ABI Issues (Largefile Support) |
1509 | |
2166 | |
|
|
2167 | Libev by default (unless the user overrides this) uses the default |
|
|
2168 | compilation environment, which means that on systems with large file |
|
|
2169 | support disabled by default, you get the 32 bit version of the stat |
|
|
2170 | structure. When using the library from programs that change the ABI to |
|
|
2171 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2172 | compile libev with the same flags to get binary compatibility. This is |
|
|
2173 | obviously the case with any flags that change the ABI, but the problem is |
|
|
2174 | most noticeably displayed with ev_stat and large file support. |
|
|
2175 | |
|
|
2176 | The solution for this is to lobby your distribution maker to make large |
|
|
2177 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2178 | optional. Libev cannot simply switch on large file support because it has |
|
|
2179 | to exchange stat structures with application programs compiled using the |
|
|
2180 | default compilation environment. |
|
|
2181 | |
|
|
2182 | =head3 Inotify and Kqueue |
|
|
2183 | |
1510 | When C<inotify (7)> support has been compiled into libev (generally only |
2184 | When C<inotify (7)> support has been compiled into libev and present at |
1511 | available on Linux) and present at runtime, it will be used to speed up |
2185 | runtime, it will be used to speed up change detection where possible. The |
1512 | change detection where possible. The inotify descriptor will be created lazily |
2186 | inotify descriptor will be created lazily when the first C<ev_stat> |
1513 | when the first C<ev_stat> watcher is being started. |
2187 | watcher is being started. |
1514 | |
2188 | |
1515 | Inotify presense does not change the semantics of C<ev_stat> watchers |
2189 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1516 | except that changes might be detected earlier, and in some cases, to avoid |
2190 | except that changes might be detected earlier, and in some cases, to avoid |
1517 | making regular C<stat> calls. Even in the presense of inotify support |
2191 | making regular C<stat> calls. Even in the presence of inotify support |
1518 | there are many cases where libev has to resort to regular C<stat> polling. |
2192 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2193 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2194 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2195 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2196 | xfs are fully working) libev usually gets away without polling. |
1519 | |
2197 | |
1520 | (There is no support for kqueue, as apparently it cannot be used to |
2198 | There is no support for kqueue, as apparently it cannot be used to |
1521 | implement this functionality, due to the requirement of having a file |
2199 | implement this functionality, due to the requirement of having a file |
1522 | descriptor open on the object at all times). |
2200 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2201 | etc. is difficult. |
|
|
2202 | |
|
|
2203 | =head3 C<stat ()> is a synchronous operation |
|
|
2204 | |
|
|
2205 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2206 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2207 | ()>, which is a synchronous operation. |
|
|
2208 | |
|
|
2209 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2210 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2211 | as the path data is usually in memory already (except when starting the |
|
|
2212 | watcher). |
|
|
2213 | |
|
|
2214 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2215 | time due to network issues, and even under good conditions, a stat call |
|
|
2216 | often takes multiple milliseconds. |
|
|
2217 | |
|
|
2218 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2219 | paths, although this is fully supported by libev. |
1523 | |
2220 | |
1524 | =head3 The special problem of stat time resolution |
2221 | =head3 The special problem of stat time resolution |
1525 | |
2222 | |
1526 | The C<stat ()> syscall only supports full-second resolution portably, and |
2223 | The C<stat ()> system call only supports full-second resolution portably, |
1527 | even on systems where the resolution is higher, many filesystems still |
2224 | and even on systems where the resolution is higher, most file systems |
1528 | only support whole seconds. |
2225 | still only support whole seconds. |
1529 | |
2226 | |
1530 | That means that, if the time is the only thing that changes, you might |
2227 | That means that, if the time is the only thing that changes, you can |
1531 | miss updates: on the first update, C<ev_stat> detects a change and calls |
2228 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1532 | your callback, which does something. When there is another update within |
2229 | calls your callback, which does something. When there is another update |
1533 | the same second, C<ev_stat> will be unable to detect it. |
2230 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2231 | stat data does change in other ways (e.g. file size). |
1534 | |
2232 | |
1535 | The solution to this is to delay acting on a change for a second (or till |
2233 | The solution to this is to delay acting on a change for slightly more |
1536 | the next second boundary), using a roughly one-second delay C<ev_timer> |
2234 | than a second (or till slightly after the next full second boundary), using |
1537 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
2235 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1538 | is added to work around small timing inconsistencies of some operating |
2236 | ev_timer_again (loop, w)>). |
1539 | systems. |
2237 | |
|
|
2238 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2239 | of some operating systems (where the second counter of the current time |
|
|
2240 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2241 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2242 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2243 | update file times then there will be a small window where the kernel uses |
|
|
2244 | the previous second to update file times but libev might already execute |
|
|
2245 | the timer callback). |
1540 | |
2246 | |
1541 | =head3 Watcher-Specific Functions and Data Members |
2247 | =head3 Watcher-Specific Functions and Data Members |
1542 | |
2248 | |
1543 | =over 4 |
2249 | =over 4 |
1544 | |
2250 | |
… | |
… | |
1550 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2256 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1551 | be detected and should normally be specified as C<0> to let libev choose |
2257 | be detected and should normally be specified as C<0> to let libev choose |
1552 | a suitable value. The memory pointed to by C<path> must point to the same |
2258 | a suitable value. The memory pointed to by C<path> must point to the same |
1553 | path for as long as the watcher is active. |
2259 | path for as long as the watcher is active. |
1554 | |
2260 | |
1555 | The callback will be receive C<EV_STAT> when a change was detected, |
2261 | The callback will receive an C<EV_STAT> event when a change was detected, |
1556 | relative to the attributes at the time the watcher was started (or the |
2262 | relative to the attributes at the time the watcher was started (or the |
1557 | last change was detected). |
2263 | last change was detected). |
1558 | |
2264 | |
1559 | =item ev_stat_stat (ev_stat *) |
2265 | =item ev_stat_stat (loop, ev_stat *) |
1560 | |
2266 | |
1561 | Updates the stat buffer immediately with new values. If you change the |
2267 | Updates the stat buffer immediately with new values. If you change the |
1562 | watched path in your callback, you could call this fucntion to avoid |
2268 | watched path in your callback, you could call this function to avoid |
1563 | detecting this change (while introducing a race condition). Can also be |
2269 | detecting this change (while introducing a race condition if you are not |
1564 | useful simply to find out the new values. |
2270 | the only one changing the path). Can also be useful simply to find out the |
|
|
2271 | new values. |
1565 | |
2272 | |
1566 | =item ev_statdata attr [read-only] |
2273 | =item ev_statdata attr [read-only] |
1567 | |
2274 | |
1568 | The most-recently detected attributes of the file. Although the type is of |
2275 | The most-recently detected attributes of the file. Although the type is |
1569 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
2276 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1570 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
2277 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2278 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1571 | was some error while C<stat>ing the file. |
2279 | some error while C<stat>ing the file. |
1572 | |
2280 | |
1573 | =item ev_statdata prev [read-only] |
2281 | =item ev_statdata prev [read-only] |
1574 | |
2282 | |
1575 | The previous attributes of the file. The callback gets invoked whenever |
2283 | The previous attributes of the file. The callback gets invoked whenever |
1576 | C<prev> != C<attr>. |
2284 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2285 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2286 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1577 | |
2287 | |
1578 | =item ev_tstamp interval [read-only] |
2288 | =item ev_tstamp interval [read-only] |
1579 | |
2289 | |
1580 | The specified interval. |
2290 | The specified interval. |
1581 | |
2291 | |
1582 | =item const char *path [read-only] |
2292 | =item const char *path [read-only] |
1583 | |
2293 | |
1584 | The filesystem path that is being watched. |
2294 | The file system path that is being watched. |
1585 | |
2295 | |
1586 | =back |
2296 | =back |
1587 | |
2297 | |
1588 | =head3 Examples |
2298 | =head3 Examples |
1589 | |
2299 | |
1590 | Example: Watch C</etc/passwd> for attribute changes. |
2300 | Example: Watch C</etc/passwd> for attribute changes. |
1591 | |
2301 | |
1592 | static void |
2302 | static void |
1593 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2303 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1594 | { |
2304 | { |
1595 | /* /etc/passwd changed in some way */ |
2305 | /* /etc/passwd changed in some way */ |
1596 | if (w->attr.st_nlink) |
2306 | if (w->attr.st_nlink) |
1597 | { |
2307 | { |
1598 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2308 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1599 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2309 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1600 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2310 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1601 | } |
2311 | } |
1602 | else |
2312 | else |
1603 | /* you shalt not abuse printf for puts */ |
2313 | /* you shalt not abuse printf for puts */ |
1604 | puts ("wow, /etc/passwd is not there, expect problems. " |
2314 | puts ("wow, /etc/passwd is not there, expect problems. " |
1605 | "if this is windows, they already arrived\n"); |
2315 | "if this is windows, they already arrived\n"); |
1606 | } |
2316 | } |
1607 | |
2317 | |
1608 | ... |
2318 | ... |
1609 | ev_stat passwd; |
2319 | ev_stat passwd; |
1610 | |
2320 | |
1611 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2321 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1612 | ev_stat_start (loop, &passwd); |
2322 | ev_stat_start (loop, &passwd); |
1613 | |
2323 | |
1614 | Example: Like above, but additionally use a one-second delay so we do not |
2324 | Example: Like above, but additionally use a one-second delay so we do not |
1615 | miss updates (however, frequent updates will delay processing, too, so |
2325 | miss updates (however, frequent updates will delay processing, too, so |
1616 | one might do the work both on C<ev_stat> callback invocation I<and> on |
2326 | one might do the work both on C<ev_stat> callback invocation I<and> on |
1617 | C<ev_timer> callback invocation). |
2327 | C<ev_timer> callback invocation). |
1618 | |
2328 | |
1619 | static ev_stat passwd; |
2329 | static ev_stat passwd; |
1620 | static ev_timer timer; |
2330 | static ev_timer timer; |
1621 | |
2331 | |
1622 | static void |
2332 | static void |
1623 | timer_cb (EV_P_ ev_timer *w, int revents) |
2333 | timer_cb (EV_P_ ev_timer *w, int revents) |
1624 | { |
2334 | { |
1625 | ev_timer_stop (EV_A_ w); |
2335 | ev_timer_stop (EV_A_ w); |
1626 | |
2336 | |
1627 | /* now it's one second after the most recent passwd change */ |
2337 | /* now it's one second after the most recent passwd change */ |
1628 | } |
2338 | } |
1629 | |
2339 | |
1630 | static void |
2340 | static void |
1631 | stat_cb (EV_P_ ev_stat *w, int revents) |
2341 | stat_cb (EV_P_ ev_stat *w, int revents) |
1632 | { |
2342 | { |
1633 | /* reset the one-second timer */ |
2343 | /* reset the one-second timer */ |
1634 | ev_timer_again (EV_A_ &timer); |
2344 | ev_timer_again (EV_A_ &timer); |
1635 | } |
2345 | } |
1636 | |
2346 | |
1637 | ... |
2347 | ... |
1638 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2348 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1639 | ev_stat_start (loop, &passwd); |
2349 | ev_stat_start (loop, &passwd); |
1640 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
2350 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1641 | |
2351 | |
1642 | |
2352 | |
1643 | =head2 C<ev_idle> - when you've got nothing better to do... |
2353 | =head2 C<ev_idle> - when you've got nothing better to do... |
1644 | |
2354 | |
1645 | Idle watchers trigger events when no other events of the same or higher |
2355 | Idle watchers trigger events when no other events of the same or higher |
1646 | priority are pending (prepare, check and other idle watchers do not |
2356 | priority are pending (prepare, check and other idle watchers do not count |
1647 | count). |
2357 | as receiving "events"). |
1648 | |
2358 | |
1649 | That is, as long as your process is busy handling sockets or timeouts |
2359 | That is, as long as your process is busy handling sockets or timeouts |
1650 | (or even signals, imagine) of the same or higher priority it will not be |
2360 | (or even signals, imagine) of the same or higher priority it will not be |
1651 | triggered. But when your process is idle (or only lower-priority watchers |
2361 | triggered. But when your process is idle (or only lower-priority watchers |
1652 | are pending), the idle watchers are being called once per event loop |
2362 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1663 | |
2373 | |
1664 | =head3 Watcher-Specific Functions and Data Members |
2374 | =head3 Watcher-Specific Functions and Data Members |
1665 | |
2375 | |
1666 | =over 4 |
2376 | =over 4 |
1667 | |
2377 | |
1668 | =item ev_idle_init (ev_signal *, callback) |
2378 | =item ev_idle_init (ev_idle *, callback) |
1669 | |
2379 | |
1670 | Initialises and configures the idle watcher - it has no parameters of any |
2380 | Initialises and configures the idle watcher - it has no parameters of any |
1671 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2381 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1672 | believe me. |
2382 | believe me. |
1673 | |
2383 | |
… | |
… | |
1676 | =head3 Examples |
2386 | =head3 Examples |
1677 | |
2387 | |
1678 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2388 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1679 | callback, free it. Also, use no error checking, as usual. |
2389 | callback, free it. Also, use no error checking, as usual. |
1680 | |
2390 | |
1681 | static void |
2391 | static void |
1682 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2392 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1683 | { |
2393 | { |
1684 | free (w); |
2394 | free (w); |
1685 | // now do something you wanted to do when the program has |
2395 | // now do something you wanted to do when the program has |
1686 | // no longer asnything immediate to do. |
2396 | // no longer anything immediate to do. |
1687 | } |
2397 | } |
1688 | |
2398 | |
1689 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2399 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1690 | ev_idle_init (idle_watcher, idle_cb); |
2400 | ev_idle_init (idle_watcher, idle_cb); |
1691 | ev_idle_start (loop, idle_cb); |
2401 | ev_idle_start (loop, idle_watcher); |
1692 | |
2402 | |
1693 | |
2403 | |
1694 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2404 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1695 | |
2405 | |
1696 | Prepare and check watchers are usually (but not always) used in tandem: |
2406 | Prepare and check watchers are usually (but not always) used in pairs: |
1697 | prepare watchers get invoked before the process blocks and check watchers |
2407 | prepare watchers get invoked before the process blocks and check watchers |
1698 | afterwards. |
2408 | afterwards. |
1699 | |
2409 | |
1700 | You I<must not> call C<ev_loop> or similar functions that enter |
2410 | You I<must not> call C<ev_loop> or similar functions that enter |
1701 | the current event loop from either C<ev_prepare> or C<ev_check> |
2411 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1704 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2414 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1705 | C<ev_check> so if you have one watcher of each kind they will always be |
2415 | C<ev_check> so if you have one watcher of each kind they will always be |
1706 | called in pairs bracketing the blocking call. |
2416 | called in pairs bracketing the blocking call. |
1707 | |
2417 | |
1708 | Their main purpose is to integrate other event mechanisms into libev and |
2418 | Their main purpose is to integrate other event mechanisms into libev and |
1709 | their use is somewhat advanced. This could be used, for example, to track |
2419 | their use is somewhat advanced. They could be used, for example, to track |
1710 | variable changes, implement your own watchers, integrate net-snmp or a |
2420 | variable changes, implement your own watchers, integrate net-snmp or a |
1711 | coroutine library and lots more. They are also occasionally useful if |
2421 | coroutine library and lots more. They are also occasionally useful if |
1712 | you cache some data and want to flush it before blocking (for example, |
2422 | you cache some data and want to flush it before blocking (for example, |
1713 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2423 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1714 | watcher). |
2424 | watcher). |
1715 | |
2425 | |
1716 | This is done by examining in each prepare call which file descriptors need |
2426 | This is done by examining in each prepare call which file descriptors |
1717 | to be watched by the other library, registering C<ev_io> watchers for |
2427 | need to be watched by the other library, registering C<ev_io> watchers |
1718 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2428 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1719 | provide just this functionality). Then, in the check watcher you check for |
2429 | libraries provide exactly this functionality). Then, in the check watcher, |
1720 | any events that occured (by checking the pending status of all watchers |
2430 | you check for any events that occurred (by checking the pending status |
1721 | and stopping them) and call back into the library. The I/O and timer |
2431 | of all watchers and stopping them) and call back into the library. The |
1722 | callbacks will never actually be called (but must be valid nevertheless, |
2432 | I/O and timer callbacks will never actually be called (but must be valid |
1723 | because you never know, you know?). |
2433 | nevertheless, because you never know, you know?). |
1724 | |
2434 | |
1725 | As another example, the Perl Coro module uses these hooks to integrate |
2435 | As another example, the Perl Coro module uses these hooks to integrate |
1726 | coroutines into libev programs, by yielding to other active coroutines |
2436 | coroutines into libev programs, by yielding to other active coroutines |
1727 | during each prepare and only letting the process block if no coroutines |
2437 | during each prepare and only letting the process block if no coroutines |
1728 | are ready to run (it's actually more complicated: it only runs coroutines |
2438 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1731 | loop from blocking if lower-priority coroutines are active, thus mapping |
2441 | loop from blocking if lower-priority coroutines are active, thus mapping |
1732 | low-priority coroutines to idle/background tasks). |
2442 | low-priority coroutines to idle/background tasks). |
1733 | |
2443 | |
1734 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2444 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1735 | priority, to ensure that they are being run before any other watchers |
2445 | priority, to ensure that they are being run before any other watchers |
|
|
2446 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2447 | |
1736 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2448 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1737 | too) should not activate ("feed") events into libev. While libev fully |
2449 | activate ("feed") events into libev. While libev fully supports this, they |
1738 | supports this, they will be called before other C<ev_check> watchers |
2450 | might get executed before other C<ev_check> watchers did their job. As |
1739 | did their job. As C<ev_check> watchers are often used to embed other |
2451 | C<ev_check> watchers are often used to embed other (non-libev) event |
1740 | (non-libev) event loops those other event loops might be in an unusable |
2452 | loops those other event loops might be in an unusable state until their |
1741 | state until their C<ev_check> watcher ran (always remind yourself to |
2453 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1742 | coexist peacefully with others). |
2454 | others). |
1743 | |
2455 | |
1744 | =head3 Watcher-Specific Functions and Data Members |
2456 | =head3 Watcher-Specific Functions and Data Members |
1745 | |
2457 | |
1746 | =over 4 |
2458 | =over 4 |
1747 | |
2459 | |
… | |
… | |
1749 | |
2461 | |
1750 | =item ev_check_init (ev_check *, callback) |
2462 | =item ev_check_init (ev_check *, callback) |
1751 | |
2463 | |
1752 | Initialises and configures the prepare or check watcher - they have no |
2464 | Initialises and configures the prepare or check watcher - they have no |
1753 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2465 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1754 | macros, but using them is utterly, utterly and completely pointless. |
2466 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2467 | pointless. |
1755 | |
2468 | |
1756 | =back |
2469 | =back |
1757 | |
2470 | |
1758 | =head3 Examples |
2471 | =head3 Examples |
1759 | |
2472 | |
1760 | There are a number of principal ways to embed other event loops or modules |
2473 | There are a number of principal ways to embed other event loops or modules |
1761 | into libev. Here are some ideas on how to include libadns into libev |
2474 | into libev. Here are some ideas on how to include libadns into libev |
1762 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
2475 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1763 | use for an actually working example. Another Perl module named C<EV::Glib> |
2476 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1764 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
2477 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1765 | into the Glib event loop). |
2478 | Glib event loop). |
1766 | |
2479 | |
1767 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
2480 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1768 | and in a check watcher, destroy them and call into libadns. What follows |
2481 | and in a check watcher, destroy them and call into libadns. What follows |
1769 | is pseudo-code only of course. This requires you to either use a low |
2482 | is pseudo-code only of course. This requires you to either use a low |
1770 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
2483 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1771 | the callbacks for the IO/timeout watchers might not have been called yet. |
2484 | the callbacks for the IO/timeout watchers might not have been called yet. |
1772 | |
2485 | |
1773 | static ev_io iow [nfd]; |
2486 | static ev_io iow [nfd]; |
1774 | static ev_timer tw; |
2487 | static ev_timer tw; |
1775 | |
2488 | |
1776 | static void |
2489 | static void |
1777 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2490 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1778 | { |
2491 | { |
1779 | } |
2492 | } |
1780 | |
2493 | |
1781 | // create io watchers for each fd and a timer before blocking |
2494 | // create io watchers for each fd and a timer before blocking |
1782 | static void |
2495 | static void |
1783 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2496 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1784 | { |
2497 | { |
1785 | int timeout = 3600000; |
2498 | int timeout = 3600000; |
1786 | struct pollfd fds [nfd]; |
2499 | struct pollfd fds [nfd]; |
1787 | // actual code will need to loop here and realloc etc. |
2500 | // actual code will need to loop here and realloc etc. |
1788 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2501 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1789 | |
2502 | |
1790 | /* the callback is illegal, but won't be called as we stop during check */ |
2503 | /* the callback is illegal, but won't be called as we stop during check */ |
1791 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2504 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1792 | ev_timer_start (loop, &tw); |
2505 | ev_timer_start (loop, &tw); |
1793 | |
2506 | |
1794 | // create one ev_io per pollfd |
2507 | // create one ev_io per pollfd |
1795 | for (int i = 0; i < nfd; ++i) |
2508 | for (int i = 0; i < nfd; ++i) |
1796 | { |
2509 | { |
1797 | ev_io_init (iow + i, io_cb, fds [i].fd, |
2510 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1798 | ((fds [i].events & POLLIN ? EV_READ : 0) |
2511 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1799 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2512 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1800 | |
2513 | |
1801 | fds [i].revents = 0; |
2514 | fds [i].revents = 0; |
1802 | ev_io_start (loop, iow + i); |
2515 | ev_io_start (loop, iow + i); |
1803 | } |
2516 | } |
1804 | } |
2517 | } |
1805 | |
2518 | |
1806 | // stop all watchers after blocking |
2519 | // stop all watchers after blocking |
1807 | static void |
2520 | static void |
1808 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2521 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1809 | { |
2522 | { |
1810 | ev_timer_stop (loop, &tw); |
2523 | ev_timer_stop (loop, &tw); |
1811 | |
2524 | |
1812 | for (int i = 0; i < nfd; ++i) |
2525 | for (int i = 0; i < nfd; ++i) |
1813 | { |
2526 | { |
1814 | // set the relevant poll flags |
2527 | // set the relevant poll flags |
1815 | // could also call adns_processreadable etc. here |
2528 | // could also call adns_processreadable etc. here |
1816 | struct pollfd *fd = fds + i; |
2529 | struct pollfd *fd = fds + i; |
1817 | int revents = ev_clear_pending (iow + i); |
2530 | int revents = ev_clear_pending (iow + i); |
1818 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
2531 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1819 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
2532 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1820 | |
2533 | |
1821 | // now stop the watcher |
2534 | // now stop the watcher |
1822 | ev_io_stop (loop, iow + i); |
2535 | ev_io_stop (loop, iow + i); |
1823 | } |
2536 | } |
1824 | |
2537 | |
1825 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2538 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1826 | } |
2539 | } |
1827 | |
2540 | |
1828 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
2541 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
1829 | in the prepare watcher and would dispose of the check watcher. |
2542 | in the prepare watcher and would dispose of the check watcher. |
1830 | |
2543 | |
1831 | Method 3: If the module to be embedded supports explicit event |
2544 | Method 3: If the module to be embedded supports explicit event |
1832 | notification (adns does), you can also make use of the actual watcher |
2545 | notification (libadns does), you can also make use of the actual watcher |
1833 | callbacks, and only destroy/create the watchers in the prepare watcher. |
2546 | callbacks, and only destroy/create the watchers in the prepare watcher. |
1834 | |
2547 | |
1835 | static void |
2548 | static void |
1836 | timer_cb (EV_P_ ev_timer *w, int revents) |
2549 | timer_cb (EV_P_ ev_timer *w, int revents) |
1837 | { |
2550 | { |
1838 | adns_state ads = (adns_state)w->data; |
2551 | adns_state ads = (adns_state)w->data; |
1839 | update_now (EV_A); |
2552 | update_now (EV_A); |
1840 | |
2553 | |
1841 | adns_processtimeouts (ads, &tv_now); |
2554 | adns_processtimeouts (ads, &tv_now); |
1842 | } |
2555 | } |
1843 | |
2556 | |
1844 | static void |
2557 | static void |
1845 | io_cb (EV_P_ ev_io *w, int revents) |
2558 | io_cb (EV_P_ ev_io *w, int revents) |
1846 | { |
2559 | { |
1847 | adns_state ads = (adns_state)w->data; |
2560 | adns_state ads = (adns_state)w->data; |
1848 | update_now (EV_A); |
2561 | update_now (EV_A); |
1849 | |
2562 | |
1850 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
2563 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
1851 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
2564 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
1852 | } |
2565 | } |
1853 | |
2566 | |
1854 | // do not ever call adns_afterpoll |
2567 | // do not ever call adns_afterpoll |
1855 | |
2568 | |
1856 | Method 4: Do not use a prepare or check watcher because the module you |
2569 | Method 4: Do not use a prepare or check watcher because the module you |
1857 | want to embed is too inflexible to support it. Instead, youc na override |
2570 | want to embed is not flexible enough to support it. Instead, you can |
1858 | their poll function. The drawback with this solution is that the main |
2571 | override their poll function. The drawback with this solution is that the |
1859 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2572 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
1860 | this. |
2573 | this approach, effectively embedding EV as a client into the horrible |
|
|
2574 | libglib event loop. |
1861 | |
2575 | |
1862 | static gint |
2576 | static gint |
1863 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2577 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
1864 | { |
2578 | { |
1865 | int got_events = 0; |
2579 | int got_events = 0; |
1866 | |
2580 | |
1867 | for (n = 0; n < nfds; ++n) |
2581 | for (n = 0; n < nfds; ++n) |
1868 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2582 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
1869 | |
2583 | |
1870 | if (timeout >= 0) |
2584 | if (timeout >= 0) |
1871 | // create/start timer |
2585 | // create/start timer |
1872 | |
2586 | |
1873 | // poll |
2587 | // poll |
1874 | ev_loop (EV_A_ 0); |
2588 | ev_loop (EV_A_ 0); |
1875 | |
2589 | |
1876 | // stop timer again |
2590 | // stop timer again |
1877 | if (timeout >= 0) |
2591 | if (timeout >= 0) |
1878 | ev_timer_stop (EV_A_ &to); |
2592 | ev_timer_stop (EV_A_ &to); |
1879 | |
2593 | |
1880 | // stop io watchers again - their callbacks should have set |
2594 | // stop io watchers again - their callbacks should have set |
1881 | for (n = 0; n < nfds; ++n) |
2595 | for (n = 0; n < nfds; ++n) |
1882 | ev_io_stop (EV_A_ iow [n]); |
2596 | ev_io_stop (EV_A_ iow [n]); |
1883 | |
2597 | |
1884 | return got_events; |
2598 | return got_events; |
1885 | } |
2599 | } |
1886 | |
2600 | |
1887 | |
2601 | |
1888 | =head2 C<ev_embed> - when one backend isn't enough... |
2602 | =head2 C<ev_embed> - when one backend isn't enough... |
1889 | |
2603 | |
1890 | This is a rather advanced watcher type that lets you embed one event loop |
2604 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
1896 | prioritise I/O. |
2610 | prioritise I/O. |
1897 | |
2611 | |
1898 | As an example for a bug workaround, the kqueue backend might only support |
2612 | As an example for a bug workaround, the kqueue backend might only support |
1899 | sockets on some platform, so it is unusable as generic backend, but you |
2613 | sockets on some platform, so it is unusable as generic backend, but you |
1900 | still want to make use of it because you have many sockets and it scales |
2614 | still want to make use of it because you have many sockets and it scales |
1901 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2615 | so nicely. In this case, you would create a kqueue-based loop and embed |
1902 | into your default loop (which might use e.g. poll). Overall operation will |
2616 | it into your default loop (which might use e.g. poll). Overall operation |
1903 | be a bit slower because first libev has to poll and then call kevent, but |
2617 | will be a bit slower because first libev has to call C<poll> and then |
1904 | at least you can use both at what they are best. |
2618 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2619 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
1905 | |
2620 | |
1906 | As for prioritising I/O: rarely you have the case where some fds have |
2621 | As for prioritising I/O: under rare circumstances you have the case where |
1907 | to be watched and handled very quickly (with low latency), and even |
2622 | some fds have to be watched and handled very quickly (with low latency), |
1908 | priorities and idle watchers might have too much overhead. In this case |
2623 | and even priorities and idle watchers might have too much overhead. In |
1909 | you would put all the high priority stuff in one loop and all the rest in |
2624 | this case you would put all the high priority stuff in one loop and all |
1910 | a second one, and embed the second one in the first. |
2625 | the rest in a second one, and embed the second one in the first. |
1911 | |
2626 | |
1912 | As long as the watcher is active, the callback will be invoked every time |
2627 | As long as the watcher is active, the callback will be invoked every |
1913 | there might be events pending in the embedded loop. The callback must then |
2628 | time there might be events pending in the embedded loop. The callback |
1914 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2629 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
1915 | their callbacks (you could also start an idle watcher to give the embedded |
2630 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
1916 | loop strictly lower priority for example). You can also set the callback |
2631 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
1917 | to C<0>, in which case the embed watcher will automatically execute the |
2632 | to give the embedded loop strictly lower priority for example). |
1918 | embedded loop sweep. |
|
|
1919 | |
2633 | |
1920 | As long as the watcher is started it will automatically handle events. The |
2634 | You can also set the callback to C<0>, in which case the embed watcher |
1921 | callback will be invoked whenever some events have been handled. You can |
2635 | will automatically execute the embedded loop sweep whenever necessary. |
1922 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
1923 | interested in that. |
|
|
1924 | |
2636 | |
1925 | Also, there have not currently been made special provisions for forking: |
2637 | Fork detection will be handled transparently while the C<ev_embed> watcher |
1926 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2638 | is active, i.e., the embedded loop will automatically be forked when the |
1927 | but you will also have to stop and restart any C<ev_embed> watchers |
2639 | embedding loop forks. In other cases, the user is responsible for calling |
1928 | yourself. |
2640 | C<ev_loop_fork> on the embedded loop. |
1929 | |
2641 | |
1930 | Unfortunately, not all backends are embeddable, only the ones returned by |
2642 | Unfortunately, not all backends are embeddable: only the ones returned by |
1931 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2643 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
1932 | portable one. |
2644 | portable one. |
1933 | |
2645 | |
1934 | So when you want to use this feature you will always have to be prepared |
2646 | So when you want to use this feature you will always have to be prepared |
1935 | that you cannot get an embeddable loop. The recommended way to get around |
2647 | that you cannot get an embeddable loop. The recommended way to get around |
1936 | this is to have a separate variables for your embeddable loop, try to |
2648 | this is to have a separate variables for your embeddable loop, try to |
1937 | create it, and if that fails, use the normal loop for everything. |
2649 | create it, and if that fails, use the normal loop for everything. |
1938 | |
2650 | |
|
|
2651 | =head3 C<ev_embed> and fork |
|
|
2652 | |
|
|
2653 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2654 | automatically be applied to the embedded loop as well, so no special |
|
|
2655 | fork handling is required in that case. When the watcher is not running, |
|
|
2656 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2657 | as applicable. |
|
|
2658 | |
1939 | =head3 Watcher-Specific Functions and Data Members |
2659 | =head3 Watcher-Specific Functions and Data Members |
1940 | |
2660 | |
1941 | =over 4 |
2661 | =over 4 |
1942 | |
2662 | |
1943 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2663 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
1946 | |
2666 | |
1947 | Configures the watcher to embed the given loop, which must be |
2667 | Configures the watcher to embed the given loop, which must be |
1948 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2668 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
1949 | invoked automatically, otherwise it is the responsibility of the callback |
2669 | invoked automatically, otherwise it is the responsibility of the callback |
1950 | to invoke it (it will continue to be called until the sweep has been done, |
2670 | to invoke it (it will continue to be called until the sweep has been done, |
1951 | if you do not want thta, you need to temporarily stop the embed watcher). |
2671 | if you do not want that, you need to temporarily stop the embed watcher). |
1952 | |
2672 | |
1953 | =item ev_embed_sweep (loop, ev_embed *) |
2673 | =item ev_embed_sweep (loop, ev_embed *) |
1954 | |
2674 | |
1955 | Make a single, non-blocking sweep over the embedded loop. This works |
2675 | Make a single, non-blocking sweep over the embedded loop. This works |
1956 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2676 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1957 | apropriate way for embedded loops. |
2677 | appropriate way for embedded loops. |
1958 | |
2678 | |
1959 | =item struct ev_loop *other [read-only] |
2679 | =item struct ev_loop *other [read-only] |
1960 | |
2680 | |
1961 | The embedded event loop. |
2681 | The embedded event loop. |
1962 | |
2682 | |
… | |
… | |
1964 | |
2684 | |
1965 | =head3 Examples |
2685 | =head3 Examples |
1966 | |
2686 | |
1967 | Example: Try to get an embeddable event loop and embed it into the default |
2687 | Example: Try to get an embeddable event loop and embed it into the default |
1968 | event loop. If that is not possible, use the default loop. The default |
2688 | event loop. If that is not possible, use the default loop. The default |
1969 | loop is stored in C<loop_hi>, while the mebeddable loop is stored in |
2689 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
1970 | C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be |
2690 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
1971 | used). |
2691 | used). |
1972 | |
2692 | |
1973 | struct ev_loop *loop_hi = ev_default_init (0); |
2693 | struct ev_loop *loop_hi = ev_default_init (0); |
1974 | struct ev_loop *loop_lo = 0; |
2694 | struct ev_loop *loop_lo = 0; |
1975 | struct ev_embed embed; |
2695 | ev_embed embed; |
1976 | |
2696 | |
1977 | // see if there is a chance of getting one that works |
2697 | // see if there is a chance of getting one that works |
1978 | // (remember that a flags value of 0 means autodetection) |
2698 | // (remember that a flags value of 0 means autodetection) |
1979 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2699 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
1980 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2700 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
1981 | : 0; |
2701 | : 0; |
1982 | |
2702 | |
1983 | // if we got one, then embed it, otherwise default to loop_hi |
2703 | // if we got one, then embed it, otherwise default to loop_hi |
1984 | if (loop_lo) |
2704 | if (loop_lo) |
1985 | { |
2705 | { |
1986 | ev_embed_init (&embed, 0, loop_lo); |
2706 | ev_embed_init (&embed, 0, loop_lo); |
1987 | ev_embed_start (loop_hi, &embed); |
2707 | ev_embed_start (loop_hi, &embed); |
1988 | } |
2708 | } |
1989 | else |
2709 | else |
1990 | loop_lo = loop_hi; |
2710 | loop_lo = loop_hi; |
1991 | |
2711 | |
1992 | Example: Check if kqueue is available but not recommended and create |
2712 | Example: Check if kqueue is available but not recommended and create |
1993 | a kqueue backend for use with sockets (which usually work with any |
2713 | a kqueue backend for use with sockets (which usually work with any |
1994 | kqueue implementation). Store the kqueue/socket-only event loop in |
2714 | kqueue implementation). Store the kqueue/socket-only event loop in |
1995 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2715 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
1996 | |
2716 | |
1997 | struct ev_loop *loop = ev_default_init (0); |
2717 | struct ev_loop *loop = ev_default_init (0); |
1998 | struct ev_loop *loop_socket = 0; |
2718 | struct ev_loop *loop_socket = 0; |
1999 | struct ev_embed embed; |
2719 | ev_embed embed; |
2000 | |
2720 | |
2001 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2721 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2002 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2722 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2003 | { |
2723 | { |
2004 | ev_embed_init (&embed, 0, loop_socket); |
2724 | ev_embed_init (&embed, 0, loop_socket); |
2005 | ev_embed_start (loop, &embed); |
2725 | ev_embed_start (loop, &embed); |
2006 | } |
2726 | } |
2007 | |
2727 | |
2008 | if (!loop_socket) |
2728 | if (!loop_socket) |
2009 | loop_socket = loop; |
2729 | loop_socket = loop; |
2010 | |
2730 | |
2011 | // now use loop_socket for all sockets, and loop for everything else |
2731 | // now use loop_socket for all sockets, and loop for everything else |
2012 | |
2732 | |
2013 | |
2733 | |
2014 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2734 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2015 | |
2735 | |
2016 | Fork watchers are called when a C<fork ()> was detected (usually because |
2736 | Fork watchers are called when a C<fork ()> was detected (usually because |
… | |
… | |
2019 | event loop blocks next and before C<ev_check> watchers are being called, |
2739 | event loop blocks next and before C<ev_check> watchers are being called, |
2020 | and only in the child after the fork. If whoever good citizen calling |
2740 | and only in the child after the fork. If whoever good citizen calling |
2021 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2741 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2022 | handlers will be invoked, too, of course. |
2742 | handlers will be invoked, too, of course. |
2023 | |
2743 | |
|
|
2744 | =head3 The special problem of life after fork - how is it possible? |
|
|
2745 | |
|
|
2746 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2747 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2748 | sequence should be handled by libev without any problems. |
|
|
2749 | |
|
|
2750 | This changes when the application actually wants to do event handling |
|
|
2751 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2752 | fork. |
|
|
2753 | |
|
|
2754 | The default mode of operation (for libev, with application help to detect |
|
|
2755 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2756 | when I<either> the parent I<or> the child process continues. |
|
|
2757 | |
|
|
2758 | When both processes want to continue using libev, then this is usually the |
|
|
2759 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2760 | supposed to continue with all watchers in place as before, while the other |
|
|
2761 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2762 | |
|
|
2763 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2764 | simply create a new event loop, which of course will be "empty", and |
|
|
2765 | use that for new watchers. This has the advantage of not touching more |
|
|
2766 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2767 | disadvantage of having to use multiple event loops (which do not support |
|
|
2768 | signal watchers). |
|
|
2769 | |
|
|
2770 | When this is not possible, or you want to use the default loop for |
|
|
2771 | other reasons, then in the process that wants to start "fresh", call |
|
|
2772 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2773 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2774 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2775 | also that in that case, you have to re-register any signal watchers. |
|
|
2776 | |
2024 | =head3 Watcher-Specific Functions and Data Members |
2777 | =head3 Watcher-Specific Functions and Data Members |
2025 | |
2778 | |
2026 | =over 4 |
2779 | =over 4 |
2027 | |
2780 | |
2028 | =item ev_fork_init (ev_signal *, callback) |
2781 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2032 | believe me. |
2785 | believe me. |
2033 | |
2786 | |
2034 | =back |
2787 | =back |
2035 | |
2788 | |
2036 | |
2789 | |
|
|
2790 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2791 | |
|
|
2792 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2793 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2794 | loops - those are of course safe to use in different threads). |
|
|
2795 | |
|
|
2796 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2797 | control, for example because it belongs to another thread. This is what |
|
|
2798 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2799 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2800 | safe. |
|
|
2801 | |
|
|
2802 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2803 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2804 | (i.e. the number of callback invocations may be less than the number of |
|
|
2805 | C<ev_async_sent> calls). |
|
|
2806 | |
|
|
2807 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2808 | just the default loop. |
|
|
2809 | |
|
|
2810 | =head3 Queueing |
|
|
2811 | |
|
|
2812 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2813 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2814 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2815 | need elaborate support such as pthreads. |
|
|
2816 | |
|
|
2817 | That means that if you want to queue data, you have to provide your own |
|
|
2818 | queue. But at least I can tell you how to implement locking around your |
|
|
2819 | queue: |
|
|
2820 | |
|
|
2821 | =over 4 |
|
|
2822 | |
|
|
2823 | =item queueing from a signal handler context |
|
|
2824 | |
|
|
2825 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2826 | handler but you block the signal handler in the watcher callback. Here is |
|
|
2827 | an example that does that for some fictitious SIGUSR1 handler: |
|
|
2828 | |
|
|
2829 | static ev_async mysig; |
|
|
2830 | |
|
|
2831 | static void |
|
|
2832 | sigusr1_handler (void) |
|
|
2833 | { |
|
|
2834 | sometype data; |
|
|
2835 | |
|
|
2836 | // no locking etc. |
|
|
2837 | queue_put (data); |
|
|
2838 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2839 | } |
|
|
2840 | |
|
|
2841 | static void |
|
|
2842 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2843 | { |
|
|
2844 | sometype data; |
|
|
2845 | sigset_t block, prev; |
|
|
2846 | |
|
|
2847 | sigemptyset (&block); |
|
|
2848 | sigaddset (&block, SIGUSR1); |
|
|
2849 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2850 | |
|
|
2851 | while (queue_get (&data)) |
|
|
2852 | process (data); |
|
|
2853 | |
|
|
2854 | if (sigismember (&prev, SIGUSR1) |
|
|
2855 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2856 | } |
|
|
2857 | |
|
|
2858 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2859 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2860 | either...). |
|
|
2861 | |
|
|
2862 | =item queueing from a thread context |
|
|
2863 | |
|
|
2864 | The strategy for threads is different, as you cannot (easily) block |
|
|
2865 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2866 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2867 | |
|
|
2868 | static ev_async mysig; |
|
|
2869 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2870 | |
|
|
2871 | static void |
|
|
2872 | otherthread (void) |
|
|
2873 | { |
|
|
2874 | // only need to lock the actual queueing operation |
|
|
2875 | pthread_mutex_lock (&mymutex); |
|
|
2876 | queue_put (data); |
|
|
2877 | pthread_mutex_unlock (&mymutex); |
|
|
2878 | |
|
|
2879 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2880 | } |
|
|
2881 | |
|
|
2882 | static void |
|
|
2883 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2884 | { |
|
|
2885 | pthread_mutex_lock (&mymutex); |
|
|
2886 | |
|
|
2887 | while (queue_get (&data)) |
|
|
2888 | process (data); |
|
|
2889 | |
|
|
2890 | pthread_mutex_unlock (&mymutex); |
|
|
2891 | } |
|
|
2892 | |
|
|
2893 | =back |
|
|
2894 | |
|
|
2895 | |
|
|
2896 | =head3 Watcher-Specific Functions and Data Members |
|
|
2897 | |
|
|
2898 | =over 4 |
|
|
2899 | |
|
|
2900 | =item ev_async_init (ev_async *, callback) |
|
|
2901 | |
|
|
2902 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2903 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
|
|
2904 | trust me. |
|
|
2905 | |
|
|
2906 | =item ev_async_send (loop, ev_async *) |
|
|
2907 | |
|
|
2908 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2909 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2910 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
|
|
2911 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2912 | section below on what exactly this means). |
|
|
2913 | |
|
|
2914 | Note that, as with other watchers in libev, multiple events might get |
|
|
2915 | compressed into a single callback invocation (another way to look at this |
|
|
2916 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2917 | reset when the event loop detects that). |
|
|
2918 | |
|
|
2919 | This call incurs the overhead of a system call only once per event loop |
|
|
2920 | iteration, so while the overhead might be noticeable, it doesn't apply to |
|
|
2921 | repeated calls to C<ev_async_send> for the same event loop. |
|
|
2922 | |
|
|
2923 | =item bool = ev_async_pending (ev_async *) |
|
|
2924 | |
|
|
2925 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2926 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2927 | event loop. |
|
|
2928 | |
|
|
2929 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2930 | the loop iterates next and checks for the watcher to have become active, |
|
|
2931 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2932 | quickly check whether invoking the loop might be a good idea. |
|
|
2933 | |
|
|
2934 | Not that this does I<not> check whether the watcher itself is pending, |
|
|
2935 | only whether it has been requested to make this watcher pending: there |
|
|
2936 | is a time window between the event loop checking and resetting the async |
|
|
2937 | notification, and the callback being invoked. |
|
|
2938 | |
|
|
2939 | =back |
|
|
2940 | |
|
|
2941 | |
2037 | =head1 OTHER FUNCTIONS |
2942 | =head1 OTHER FUNCTIONS |
2038 | |
2943 | |
2039 | There are some other functions of possible interest. Described. Here. Now. |
2944 | There are some other functions of possible interest. Described. Here. Now. |
2040 | |
2945 | |
2041 | =over 4 |
2946 | =over 4 |
2042 | |
2947 | |
2043 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2948 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2044 | |
2949 | |
2045 | This function combines a simple timer and an I/O watcher, calls your |
2950 | This function combines a simple timer and an I/O watcher, calls your |
2046 | callback on whichever event happens first and automatically stop both |
2951 | callback on whichever event happens first and automatically stops both |
2047 | watchers. This is useful if you want to wait for a single event on an fd |
2952 | watchers. This is useful if you want to wait for a single event on an fd |
2048 | or timeout without having to allocate/configure/start/stop/free one or |
2953 | or timeout without having to allocate/configure/start/stop/free one or |
2049 | more watchers yourself. |
2954 | more watchers yourself. |
2050 | |
2955 | |
2051 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2956 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2052 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2957 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2053 | C<events> set will be craeted and started. |
2958 | the given C<fd> and C<events> set will be created and started. |
2054 | |
2959 | |
2055 | If C<timeout> is less than 0, then no timeout watcher will be |
2960 | If C<timeout> is less than 0, then no timeout watcher will be |
2056 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2961 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2057 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2962 | repeat = 0) will be started. C<0> is a valid timeout. |
2058 | dubious value. |
|
|
2059 | |
2963 | |
2060 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2964 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2061 | passed an C<revents> set like normal event callbacks (a combination of |
2965 | passed an C<revents> set like normal event callbacks (a combination of |
2062 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2966 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2063 | value passed to C<ev_once>: |
2967 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2968 | a timeout and an io event at the same time - you probably should give io |
|
|
2969 | events precedence. |
2064 | |
2970 | |
|
|
2971 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
2972 | |
2065 | static void stdin_ready (int revents, void *arg) |
2973 | static void stdin_ready (int revents, void *arg) |
2066 | { |
2974 | { |
2067 | if (revents & EV_TIMEOUT) |
|
|
2068 | /* doh, nothing entered */; |
|
|
2069 | else if (revents & EV_READ) |
2975 | if (revents & EV_READ) |
2070 | /* stdin might have data for us, joy! */; |
2976 | /* stdin might have data for us, joy! */; |
|
|
2977 | else if (revents & EV_TIMEOUT) |
|
|
2978 | /* doh, nothing entered */; |
2071 | } |
2979 | } |
2072 | |
2980 | |
2073 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2981 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2074 | |
2982 | |
2075 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2983 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2076 | |
2984 | |
2077 | Feeds the given event set into the event loop, as if the specified event |
2985 | Feeds the given event set into the event loop, as if the specified event |
2078 | had happened for the specified watcher (which must be a pointer to an |
2986 | had happened for the specified watcher (which must be a pointer to an |
2079 | initialised but not necessarily started event watcher). |
2987 | initialised but not necessarily started event watcher). |
2080 | |
2988 | |
2081 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2989 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2082 | |
2990 | |
2083 | Feed an event on the given fd, as if a file descriptor backend detected |
2991 | Feed an event on the given fd, as if a file descriptor backend detected |
2084 | the given events it. |
2992 | the given events it. |
2085 | |
2993 | |
2086 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2994 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2087 | |
2995 | |
2088 | Feed an event as if the given signal occured (C<loop> must be the default |
2996 | Feed an event as if the given signal occurred (C<loop> must be the default |
2089 | loop!). |
2997 | loop!). |
2090 | |
2998 | |
2091 | =back |
2999 | =back |
2092 | |
3000 | |
2093 | |
3001 | |
… | |
… | |
2109 | |
3017 | |
2110 | =item * Priorities are not currently supported. Initialising priorities |
3018 | =item * Priorities are not currently supported. Initialising priorities |
2111 | will fail and all watchers will have the same priority, even though there |
3019 | will fail and all watchers will have the same priority, even though there |
2112 | is an ev_pri field. |
3020 | is an ev_pri field. |
2113 | |
3021 | |
|
|
3022 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
3023 | first base created (== the default loop) gets the signals. |
|
|
3024 | |
2114 | =item * Other members are not supported. |
3025 | =item * Other members are not supported. |
2115 | |
3026 | |
2116 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3027 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2117 | to use the libev header file and library. |
3028 | to use the libev header file and library. |
2118 | |
3029 | |
2119 | =back |
3030 | =back |
2120 | |
3031 | |
2121 | =head1 C++ SUPPORT |
3032 | =head1 C++ SUPPORT |
2122 | |
3033 | |
2123 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3034 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2124 | you to use some convinience methods to start/stop watchers and also change |
3035 | you to use some convenience methods to start/stop watchers and also change |
2125 | the callback model to a model using method callbacks on objects. |
3036 | the callback model to a model using method callbacks on objects. |
2126 | |
3037 | |
2127 | To use it, |
3038 | To use it, |
2128 | |
3039 | |
2129 | #include <ev++.h> |
3040 | #include <ev++.h> |
2130 | |
3041 | |
2131 | This automatically includes F<ev.h> and puts all of its definitions (many |
3042 | This automatically includes F<ev.h> and puts all of its definitions (many |
2132 | of them macros) into the global namespace. All C++ specific things are |
3043 | of them macros) into the global namespace. All C++ specific things are |
2133 | put into the C<ev> namespace. It should support all the same embedding |
3044 | put into the C<ev> namespace. It should support all the same embedding |
2134 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
3045 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
2201 | your compiler is good :), then the method will be fully inlined into the |
3112 | your compiler is good :), then the method will be fully inlined into the |
2202 | thunking function, making it as fast as a direct C callback. |
3113 | thunking function, making it as fast as a direct C callback. |
2203 | |
3114 | |
2204 | Example: simple class declaration and watcher initialisation |
3115 | Example: simple class declaration and watcher initialisation |
2205 | |
3116 | |
2206 | struct myclass |
3117 | struct myclass |
2207 | { |
3118 | { |
2208 | void io_cb (ev::io &w, int revents) { } |
3119 | void io_cb (ev::io &w, int revents) { } |
2209 | } |
3120 | } |
2210 | |
3121 | |
2211 | myclass obj; |
3122 | myclass obj; |
2212 | ev::io iow; |
3123 | ev::io iow; |
2213 | iow.set <myclass, &myclass::io_cb> (&obj); |
3124 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3125 | |
|
|
3126 | =item w->set (object *) |
|
|
3127 | |
|
|
3128 | This is an B<experimental> feature that might go away in a future version. |
|
|
3129 | |
|
|
3130 | This is a variation of a method callback - leaving out the method to call |
|
|
3131 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3132 | functor objects without having to manually specify the C<operator ()> all |
|
|
3133 | the time. Incidentally, you can then also leave out the template argument |
|
|
3134 | list. |
|
|
3135 | |
|
|
3136 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3137 | int revents)>. |
|
|
3138 | |
|
|
3139 | See the method-C<set> above for more details. |
|
|
3140 | |
|
|
3141 | Example: use a functor object as callback. |
|
|
3142 | |
|
|
3143 | struct myfunctor |
|
|
3144 | { |
|
|
3145 | void operator() (ev::io &w, int revents) |
|
|
3146 | { |
|
|
3147 | ... |
|
|
3148 | } |
|
|
3149 | } |
|
|
3150 | |
|
|
3151 | myfunctor f; |
|
|
3152 | |
|
|
3153 | ev::io w; |
|
|
3154 | w.set (&f); |
2214 | |
3155 | |
2215 | =item w->set<function> (void *data = 0) |
3156 | =item w->set<function> (void *data = 0) |
2216 | |
3157 | |
2217 | Also sets a callback, but uses a static method or plain function as |
3158 | Also sets a callback, but uses a static method or plain function as |
2218 | callback. The optional C<data> argument will be stored in the watcher's |
3159 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2220 | |
3161 | |
2221 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3162 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2222 | |
3163 | |
2223 | See the method-C<set> above for more details. |
3164 | See the method-C<set> above for more details. |
2224 | |
3165 | |
2225 | Example: |
3166 | Example: Use a plain function as callback. |
2226 | |
3167 | |
2227 | static void io_cb (ev::io &w, int revents) { } |
3168 | static void io_cb (ev::io &w, int revents) { } |
2228 | iow.set <io_cb> (); |
3169 | iow.set <io_cb> (); |
2229 | |
3170 | |
2230 | =item w->set (struct ev_loop *) |
3171 | =item w->set (struct ev_loop *) |
2231 | |
3172 | |
2232 | Associates a different C<struct ev_loop> with this watcher. You can only |
3173 | Associates a different C<struct ev_loop> with this watcher. You can only |
2233 | do this when the watcher is inactive (and not pending either). |
3174 | do this when the watcher is inactive (and not pending either). |
2234 | |
3175 | |
2235 | =item w->set ([args]) |
3176 | =item w->set ([arguments]) |
2236 | |
3177 | |
2237 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
3178 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
2238 | called at least once. Unlike the C counterpart, an active watcher gets |
3179 | called at least once. Unlike the C counterpart, an active watcher gets |
2239 | automatically stopped and restarted when reconfiguring it with this |
3180 | automatically stopped and restarted when reconfiguring it with this |
2240 | method. |
3181 | method. |
2241 | |
3182 | |
2242 | =item w->start () |
3183 | =item w->start () |
… | |
… | |
2266 | =back |
3207 | =back |
2267 | |
3208 | |
2268 | Example: Define a class with an IO and idle watcher, start one of them in |
3209 | Example: Define a class with an IO and idle watcher, start one of them in |
2269 | the constructor. |
3210 | the constructor. |
2270 | |
3211 | |
2271 | class myclass |
3212 | class myclass |
2272 | { |
3213 | { |
2273 | ev_io io; void io_cb (ev::io &w, int revents); |
3214 | ev::io io ; void io_cb (ev::io &w, int revents); |
2274 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
3215 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2275 | |
3216 | |
2276 | myclass (); |
3217 | myclass (int fd) |
2277 | } |
3218 | { |
2278 | |
|
|
2279 | myclass::myclass (int fd) |
|
|
2280 | { |
|
|
2281 | io .set <myclass, &myclass::io_cb > (this); |
3219 | io .set <myclass, &myclass::io_cb > (this); |
2282 | idle.set <myclass, &myclass::idle_cb> (this); |
3220 | idle.set <myclass, &myclass::idle_cb> (this); |
2283 | |
3221 | |
2284 | io.start (fd, ev::READ); |
3222 | io.start (fd, ev::READ); |
|
|
3223 | } |
2285 | } |
3224 | }; |
|
|
3225 | |
|
|
3226 | |
|
|
3227 | =head1 OTHER LANGUAGE BINDINGS |
|
|
3228 | |
|
|
3229 | Libev does not offer other language bindings itself, but bindings for a |
|
|
3230 | number of languages exist in the form of third-party packages. If you know |
|
|
3231 | any interesting language binding in addition to the ones listed here, drop |
|
|
3232 | me a note. |
|
|
3233 | |
|
|
3234 | =over 4 |
|
|
3235 | |
|
|
3236 | =item Perl |
|
|
3237 | |
|
|
3238 | The EV module implements the full libev API and is actually used to test |
|
|
3239 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
3240 | there are additional modules that implement libev-compatible interfaces |
|
|
3241 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
|
|
3242 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3243 | and C<EV::Glib>). |
|
|
3244 | |
|
|
3245 | It can be found and installed via CPAN, its homepage is at |
|
|
3246 | L<http://software.schmorp.de/pkg/EV>. |
|
|
3247 | |
|
|
3248 | =item Python |
|
|
3249 | |
|
|
3250 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
3251 | seems to be quite complete and well-documented. |
|
|
3252 | |
|
|
3253 | =item Ruby |
|
|
3254 | |
|
|
3255 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
3256 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
3257 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
3258 | L<http://rev.rubyforge.org/>. |
|
|
3259 | |
|
|
3260 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3261 | makes rev work even on mingw. |
|
|
3262 | |
|
|
3263 | =item Haskell |
|
|
3264 | |
|
|
3265 | A haskell binding to libev is available at |
|
|
3266 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3267 | |
|
|
3268 | =item D |
|
|
3269 | |
|
|
3270 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
3271 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3272 | |
|
|
3273 | =item Ocaml |
|
|
3274 | |
|
|
3275 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3276 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3277 | |
|
|
3278 | =back |
2286 | |
3279 | |
2287 | |
3280 | |
2288 | =head1 MACRO MAGIC |
3281 | =head1 MACRO MAGIC |
2289 | |
3282 | |
2290 | Libev can be compiled with a variety of options, the most fundamantal |
3283 | Libev can be compiled with a variety of options, the most fundamental |
2291 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
3284 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2292 | functions and callbacks have an initial C<struct ev_loop *> argument. |
3285 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2293 | |
3286 | |
2294 | To make it easier to write programs that cope with either variant, the |
3287 | To make it easier to write programs that cope with either variant, the |
2295 | following macros are defined: |
3288 | following macros are defined: |
… | |
… | |
2300 | |
3293 | |
2301 | This provides the loop I<argument> for functions, if one is required ("ev |
3294 | This provides the loop I<argument> for functions, if one is required ("ev |
2302 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3295 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2303 | C<EV_A_> is used when other arguments are following. Example: |
3296 | C<EV_A_> is used when other arguments are following. Example: |
2304 | |
3297 | |
2305 | ev_unref (EV_A); |
3298 | ev_unref (EV_A); |
2306 | ev_timer_add (EV_A_ watcher); |
3299 | ev_timer_add (EV_A_ watcher); |
2307 | ev_loop (EV_A_ 0); |
3300 | ev_loop (EV_A_ 0); |
2308 | |
3301 | |
2309 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3302 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2310 | which is often provided by the following macro. |
3303 | which is often provided by the following macro. |
2311 | |
3304 | |
2312 | =item C<EV_P>, C<EV_P_> |
3305 | =item C<EV_P>, C<EV_P_> |
2313 | |
3306 | |
2314 | This provides the loop I<parameter> for functions, if one is required ("ev |
3307 | This provides the loop I<parameter> for functions, if one is required ("ev |
2315 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
3308 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
2316 | C<EV_P_> is used when other parameters are following. Example: |
3309 | C<EV_P_> is used when other parameters are following. Example: |
2317 | |
3310 | |
2318 | // this is how ev_unref is being declared |
3311 | // this is how ev_unref is being declared |
2319 | static void ev_unref (EV_P); |
3312 | static void ev_unref (EV_P); |
2320 | |
3313 | |
2321 | // this is how you can declare your typical callback |
3314 | // this is how you can declare your typical callback |
2322 | static void cb (EV_P_ ev_timer *w, int revents) |
3315 | static void cb (EV_P_ ev_timer *w, int revents) |
2323 | |
3316 | |
2324 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
3317 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
2325 | suitable for use with C<EV_A>. |
3318 | suitable for use with C<EV_A>. |
2326 | |
3319 | |
2327 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3320 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2328 | |
3321 | |
2329 | Similar to the other two macros, this gives you the value of the default |
3322 | Similar to the other two macros, this gives you the value of the default |
2330 | loop, if multiple loops are supported ("ev loop default"). |
3323 | loop, if multiple loops are supported ("ev loop default"). |
|
|
3324 | |
|
|
3325 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
3326 | |
|
|
3327 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
3328 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
3329 | is undefined when the default loop has not been initialised by a previous |
|
|
3330 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
3331 | |
|
|
3332 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
3333 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2331 | |
3334 | |
2332 | =back |
3335 | =back |
2333 | |
3336 | |
2334 | Example: Declare and initialise a check watcher, utilising the above |
3337 | Example: Declare and initialise a check watcher, utilising the above |
2335 | macros so it will work regardless of whether multiple loops are supported |
3338 | macros so it will work regardless of whether multiple loops are supported |
2336 | or not. |
3339 | or not. |
2337 | |
3340 | |
2338 | static void |
3341 | static void |
2339 | check_cb (EV_P_ ev_timer *w, int revents) |
3342 | check_cb (EV_P_ ev_timer *w, int revents) |
2340 | { |
3343 | { |
2341 | ev_check_stop (EV_A_ w); |
3344 | ev_check_stop (EV_A_ w); |
2342 | } |
3345 | } |
2343 | |
3346 | |
2344 | ev_check check; |
3347 | ev_check check; |
2345 | ev_check_init (&check, check_cb); |
3348 | ev_check_init (&check, check_cb); |
2346 | ev_check_start (EV_DEFAULT_ &check); |
3349 | ev_check_start (EV_DEFAULT_ &check); |
2347 | ev_loop (EV_DEFAULT_ 0); |
3350 | ev_loop (EV_DEFAULT_ 0); |
2348 | |
3351 | |
2349 | =head1 EMBEDDING |
3352 | =head1 EMBEDDING |
2350 | |
3353 | |
2351 | Libev can (and often is) directly embedded into host |
3354 | Libev can (and often is) directly embedded into host |
2352 | applications. Examples of applications that embed it include the Deliantra |
3355 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2359 | libev somewhere in your source tree). |
3362 | libev somewhere in your source tree). |
2360 | |
3363 | |
2361 | =head2 FILESETS |
3364 | =head2 FILESETS |
2362 | |
3365 | |
2363 | Depending on what features you need you need to include one or more sets of files |
3366 | Depending on what features you need you need to include one or more sets of files |
2364 | in your app. |
3367 | in your application. |
2365 | |
3368 | |
2366 | =head3 CORE EVENT LOOP |
3369 | =head3 CORE EVENT LOOP |
2367 | |
3370 | |
2368 | To include only the libev core (all the C<ev_*> functions), with manual |
3371 | To include only the libev core (all the C<ev_*> functions), with manual |
2369 | configuration (no autoconf): |
3372 | configuration (no autoconf): |
2370 | |
3373 | |
2371 | #define EV_STANDALONE 1 |
3374 | #define EV_STANDALONE 1 |
2372 | #include "ev.c" |
3375 | #include "ev.c" |
2373 | |
3376 | |
2374 | This will automatically include F<ev.h>, too, and should be done in a |
3377 | This will automatically include F<ev.h>, too, and should be done in a |
2375 | single C source file only to provide the function implementations. To use |
3378 | single C source file only to provide the function implementations. To use |
2376 | it, do the same for F<ev.h> in all files wishing to use this API (best |
3379 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2377 | done by writing a wrapper around F<ev.h> that you can include instead and |
3380 | done by writing a wrapper around F<ev.h> that you can include instead and |
2378 | where you can put other configuration options): |
3381 | where you can put other configuration options): |
2379 | |
3382 | |
2380 | #define EV_STANDALONE 1 |
3383 | #define EV_STANDALONE 1 |
2381 | #include "ev.h" |
3384 | #include "ev.h" |
2382 | |
3385 | |
2383 | Both header files and implementation files can be compiled with a C++ |
3386 | Both header files and implementation files can be compiled with a C++ |
2384 | compiler (at least, thats a stated goal, and breakage will be treated |
3387 | compiler (at least, that's a stated goal, and breakage will be treated |
2385 | as a bug). |
3388 | as a bug). |
2386 | |
3389 | |
2387 | You need the following files in your source tree, or in a directory |
3390 | You need the following files in your source tree, or in a directory |
2388 | in your include path (e.g. in libev/ when using -Ilibev): |
3391 | in your include path (e.g. in libev/ when using -Ilibev): |
2389 | |
3392 | |
2390 | ev.h |
3393 | ev.h |
2391 | ev.c |
3394 | ev.c |
2392 | ev_vars.h |
3395 | ev_vars.h |
2393 | ev_wrap.h |
3396 | ev_wrap.h |
2394 | |
3397 | |
2395 | ev_win32.c required on win32 platforms only |
3398 | ev_win32.c required on win32 platforms only |
2396 | |
3399 | |
2397 | ev_select.c only when select backend is enabled (which is enabled by default) |
3400 | ev_select.c only when select backend is enabled (which is enabled by default) |
2398 | ev_poll.c only when poll backend is enabled (disabled by default) |
3401 | ev_poll.c only when poll backend is enabled (disabled by default) |
2399 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
3402 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2400 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
3403 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2401 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
3404 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2402 | |
3405 | |
2403 | F<ev.c> includes the backend files directly when enabled, so you only need |
3406 | F<ev.c> includes the backend files directly when enabled, so you only need |
2404 | to compile this single file. |
3407 | to compile this single file. |
2405 | |
3408 | |
2406 | =head3 LIBEVENT COMPATIBILITY API |
3409 | =head3 LIBEVENT COMPATIBILITY API |
2407 | |
3410 | |
2408 | To include the libevent compatibility API, also include: |
3411 | To include the libevent compatibility API, also include: |
2409 | |
3412 | |
2410 | #include "event.c" |
3413 | #include "event.c" |
2411 | |
3414 | |
2412 | in the file including F<ev.c>, and: |
3415 | in the file including F<ev.c>, and: |
2413 | |
3416 | |
2414 | #include "event.h" |
3417 | #include "event.h" |
2415 | |
3418 | |
2416 | in the files that want to use the libevent API. This also includes F<ev.h>. |
3419 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2417 | |
3420 | |
2418 | You need the following additional files for this: |
3421 | You need the following additional files for this: |
2419 | |
3422 | |
2420 | event.h |
3423 | event.h |
2421 | event.c |
3424 | event.c |
2422 | |
3425 | |
2423 | =head3 AUTOCONF SUPPORT |
3426 | =head3 AUTOCONF SUPPORT |
2424 | |
3427 | |
2425 | Instead of using C<EV_STANDALONE=1> and providing your config in |
3428 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2426 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
3429 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2427 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
3430 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2428 | include F<config.h> and configure itself accordingly. |
3431 | include F<config.h> and configure itself accordingly. |
2429 | |
3432 | |
2430 | For this of course you need the m4 file: |
3433 | For this of course you need the m4 file: |
2431 | |
3434 | |
2432 | libev.m4 |
3435 | libev.m4 |
2433 | |
3436 | |
2434 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3437 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2435 | |
3438 | |
2436 | Libev can be configured via a variety of preprocessor symbols you have to define |
3439 | Libev can be configured via a variety of preprocessor symbols you have to |
2437 | before including any of its files. The default is not to build for multiplicity |
3440 | define before including any of its files. The default in the absence of |
2438 | and only include the select backend. |
3441 | autoconf is documented for every option. |
2439 | |
3442 | |
2440 | =over 4 |
3443 | =over 4 |
2441 | |
3444 | |
2442 | =item EV_STANDALONE |
3445 | =item EV_STANDALONE |
2443 | |
3446 | |
… | |
… | |
2445 | keeps libev from including F<config.h>, and it also defines dummy |
3448 | keeps libev from including F<config.h>, and it also defines dummy |
2446 | implementations for some libevent functions (such as logging, which is not |
3449 | implementations for some libevent functions (such as logging, which is not |
2447 | supported). It will also not define any of the structs usually found in |
3450 | supported). It will also not define any of the structs usually found in |
2448 | F<event.h> that are not directly supported by the libev core alone. |
3451 | F<event.h> that are not directly supported by the libev core alone. |
2449 | |
3452 | |
|
|
3453 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3454 | configuration, but has to be more conservative. |
|
|
3455 | |
2450 | =item EV_USE_MONOTONIC |
3456 | =item EV_USE_MONOTONIC |
2451 | |
3457 | |
2452 | If defined to be C<1>, libev will try to detect the availability of the |
3458 | If defined to be C<1>, libev will try to detect the availability of the |
2453 | monotonic clock option at both compiletime and runtime. Otherwise no use |
3459 | monotonic clock option at both compile time and runtime. Otherwise no |
2454 | of the monotonic clock option will be attempted. If you enable this, you |
3460 | use of the monotonic clock option will be attempted. If you enable this, |
2455 | usually have to link against librt or something similar. Enabling it when |
3461 | you usually have to link against librt or something similar. Enabling it |
2456 | the functionality isn't available is safe, though, although you have |
3462 | when the functionality isn't available is safe, though, although you have |
2457 | to make sure you link against any libraries where the C<clock_gettime> |
3463 | to make sure you link against any libraries where the C<clock_gettime> |
2458 | function is hiding in (often F<-lrt>). |
3464 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2459 | |
3465 | |
2460 | =item EV_USE_REALTIME |
3466 | =item EV_USE_REALTIME |
2461 | |
3467 | |
2462 | If defined to be C<1>, libev will try to detect the availability of the |
3468 | If defined to be C<1>, libev will try to detect the availability of the |
2463 | realtime clock option at compiletime (and assume its availability at |
3469 | real-time clock option at compile time (and assume its availability |
2464 | runtime if successful). Otherwise no use of the realtime clock option will |
3470 | at runtime if successful). Otherwise no use of the real-time clock |
2465 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3471 | option will be attempted. This effectively replaces C<gettimeofday> |
2466 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3472 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2467 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3473 | correctness. See the note about libraries in the description of |
|
|
3474 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3475 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3476 | |
|
|
3477 | =item EV_USE_CLOCK_SYSCALL |
|
|
3478 | |
|
|
3479 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3480 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3481 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3482 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3483 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3484 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3485 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3486 | higher, as it simplifies linking (no need for C<-lrt>). |
2468 | |
3487 | |
2469 | =item EV_USE_NANOSLEEP |
3488 | =item EV_USE_NANOSLEEP |
2470 | |
3489 | |
2471 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3490 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2472 | and will use it for delays. Otherwise it will use C<select ()>. |
3491 | and will use it for delays. Otherwise it will use C<select ()>. |
2473 | |
3492 | |
|
|
3493 | =item EV_USE_EVENTFD |
|
|
3494 | |
|
|
3495 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
3496 | available and will probe for kernel support at runtime. This will improve |
|
|
3497 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
3498 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3499 | 2.7 or newer, otherwise disabled. |
|
|
3500 | |
2474 | =item EV_USE_SELECT |
3501 | =item EV_USE_SELECT |
2475 | |
3502 | |
2476 | If undefined or defined to be C<1>, libev will compile in support for the |
3503 | If undefined or defined to be C<1>, libev will compile in support for the |
2477 | C<select>(2) backend. No attempt at autodetection will be done: if no |
3504 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
2478 | other method takes over, select will be it. Otherwise the select backend |
3505 | other method takes over, select will be it. Otherwise the select backend |
2479 | will not be compiled in. |
3506 | will not be compiled in. |
2480 | |
3507 | |
2481 | =item EV_SELECT_USE_FD_SET |
3508 | =item EV_SELECT_USE_FD_SET |
2482 | |
3509 | |
2483 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3510 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2484 | structure. This is useful if libev doesn't compile due to a missing |
3511 | structure. This is useful if libev doesn't compile due to a missing |
2485 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
3512 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2486 | exotic systems. This usually limits the range of file descriptors to some |
3513 | on exotic systems. This usually limits the range of file descriptors to |
2487 | low limit such as 1024 or might have other limitations (winsocket only |
3514 | some low limit such as 1024 or might have other limitations (winsocket |
2488 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3515 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2489 | influence the size of the C<fd_set> used. |
3516 | configures the maximum size of the C<fd_set>. |
2490 | |
3517 | |
2491 | =item EV_SELECT_IS_WINSOCKET |
3518 | =item EV_SELECT_IS_WINSOCKET |
2492 | |
3519 | |
2493 | When defined to C<1>, the select backend will assume that |
3520 | When defined to C<1>, the select backend will assume that |
2494 | select/socket/connect etc. don't understand file descriptors but |
3521 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2514 | |
3541 | |
2515 | =item EV_USE_EPOLL |
3542 | =item EV_USE_EPOLL |
2516 | |
3543 | |
2517 | If defined to be C<1>, libev will compile in support for the Linux |
3544 | If defined to be C<1>, libev will compile in support for the Linux |
2518 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3545 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2519 | otherwise another method will be used as fallback. This is the |
3546 | otherwise another method will be used as fallback. This is the preferred |
2520 | preferred backend for GNU/Linux systems. |
3547 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3548 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2521 | |
3549 | |
2522 | =item EV_USE_KQUEUE |
3550 | =item EV_USE_KQUEUE |
2523 | |
3551 | |
2524 | If defined to be C<1>, libev will compile in support for the BSD style |
3552 | If defined to be C<1>, libev will compile in support for the BSD style |
2525 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
3553 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2538 | otherwise another method will be used as fallback. This is the preferred |
3566 | otherwise another method will be used as fallback. This is the preferred |
2539 | backend for Solaris 10 systems. |
3567 | backend for Solaris 10 systems. |
2540 | |
3568 | |
2541 | =item EV_USE_DEVPOLL |
3569 | =item EV_USE_DEVPOLL |
2542 | |
3570 | |
2543 | reserved for future expansion, works like the USE symbols above. |
3571 | Reserved for future expansion, works like the USE symbols above. |
2544 | |
3572 | |
2545 | =item EV_USE_INOTIFY |
3573 | =item EV_USE_INOTIFY |
2546 | |
3574 | |
2547 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3575 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2548 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3576 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2549 | be detected at runtime. |
3577 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3578 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3579 | |
|
|
3580 | =item EV_ATOMIC_T |
|
|
3581 | |
|
|
3582 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
3583 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3584 | type is easily found in the C language, so you can provide your own type |
|
|
3585 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
3586 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3587 | |
|
|
3588 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3589 | (from F<signal.h>), which is usually good enough on most platforms. |
2550 | |
3590 | |
2551 | =item EV_H |
3591 | =item EV_H |
2552 | |
3592 | |
2553 | The name of the F<ev.h> header file used to include it. The default if |
3593 | The name of the F<ev.h> header file used to include it. The default if |
2554 | undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to |
3594 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2555 | virtually rename the F<ev.h> header file in case of conflicts. |
3595 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2556 | |
3596 | |
2557 | =item EV_CONFIG_H |
3597 | =item EV_CONFIG_H |
2558 | |
3598 | |
2559 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3599 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2560 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3600 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2561 | C<EV_H>, above. |
3601 | C<EV_H>, above. |
2562 | |
3602 | |
2563 | =item EV_EVENT_H |
3603 | =item EV_EVENT_H |
2564 | |
3604 | |
2565 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3605 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2566 | of how the F<event.h> header can be found, the dfeault is C<"event.h">. |
3606 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2567 | |
3607 | |
2568 | =item EV_PROTOTYPES |
3608 | =item EV_PROTOTYPES |
2569 | |
3609 | |
2570 | If defined to be C<0>, then F<ev.h> will not define any function |
3610 | If defined to be C<0>, then F<ev.h> will not define any function |
2571 | prototypes, but still define all the structs and other symbols. This is |
3611 | prototypes, but still define all the structs and other symbols. This is |
… | |
… | |
2592 | When doing priority-based operations, libev usually has to linearly search |
3632 | When doing priority-based operations, libev usually has to linearly search |
2593 | all the priorities, so having many of them (hundreds) uses a lot of space |
3633 | all the priorities, so having many of them (hundreds) uses a lot of space |
2594 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3634 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2595 | fine. |
3635 | fine. |
2596 | |
3636 | |
2597 | If your embedding app does not need any priorities, defining these both to |
3637 | If your embedding application does not need any priorities, defining these |
2598 | C<0> will save some memory and cpu. |
3638 | both to C<0> will save some memory and CPU. |
2599 | |
3639 | |
2600 | =item EV_PERIODIC_ENABLE |
3640 | =item EV_PERIODIC_ENABLE |
2601 | |
3641 | |
2602 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3642 | If undefined or defined to be C<1>, then periodic timers are supported. If |
2603 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3643 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
2610 | code. |
3650 | code. |
2611 | |
3651 | |
2612 | =item EV_EMBED_ENABLE |
3652 | =item EV_EMBED_ENABLE |
2613 | |
3653 | |
2614 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3654 | If undefined or defined to be C<1>, then embed watchers are supported. If |
2615 | defined to be C<0>, then they are not. |
3655 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3656 | watcher types, which therefore must not be disabled. |
2616 | |
3657 | |
2617 | =item EV_STAT_ENABLE |
3658 | =item EV_STAT_ENABLE |
2618 | |
3659 | |
2619 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3660 | If undefined or defined to be C<1>, then stat watchers are supported. If |
2620 | defined to be C<0>, then they are not. |
3661 | defined to be C<0>, then they are not. |
… | |
… | |
2622 | =item EV_FORK_ENABLE |
3663 | =item EV_FORK_ENABLE |
2623 | |
3664 | |
2624 | If undefined or defined to be C<1>, then fork watchers are supported. If |
3665 | If undefined or defined to be C<1>, then fork watchers are supported. If |
2625 | defined to be C<0>, then they are not. |
3666 | defined to be C<0>, then they are not. |
2626 | |
3667 | |
|
|
3668 | =item EV_ASYNC_ENABLE |
|
|
3669 | |
|
|
3670 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3671 | defined to be C<0>, then they are not. |
|
|
3672 | |
2627 | =item EV_MINIMAL |
3673 | =item EV_MINIMAL |
2628 | |
3674 | |
2629 | If you need to shave off some kilobytes of code at the expense of some |
3675 | If you need to shave off some kilobytes of code at the expense of some |
2630 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3676 | speed (but with the full API), define this symbol to C<1>. Currently this |
2631 | some inlining decisions, saves roughly 30% codesize of amd64. |
3677 | is used to override some inlining decisions, saves roughly 30% code size |
|
|
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3679 | the default 4-heap. |
|
|
3680 | |
|
|
3681 | You can save even more by disabling watcher types you do not need and |
|
|
3682 | setting C<EV_MAXPRI> == C<EV_MINPRI>. |
2632 | |
3683 | |
2633 | =item EV_PID_HASHSIZE |
3684 | =item EV_PID_HASHSIZE |
2634 | |
3685 | |
2635 | C<ev_child> watchers use a small hash table to distribute workload by |
3686 | C<ev_child> watchers use a small hash table to distribute workload by |
2636 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3687 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2643 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3694 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2644 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3695 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2645 | watchers you might want to increase this value (I<must> be a power of |
3696 | watchers you might want to increase this value (I<must> be a power of |
2646 | two). |
3697 | two). |
2647 | |
3698 | |
|
|
3699 | =item EV_USE_4HEAP |
|
|
3700 | |
|
|
3701 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3702 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
3703 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
3704 | faster performance with many (thousands) of watchers. |
|
|
3705 | |
|
|
3706 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3707 | (disabled). |
|
|
3708 | |
|
|
3709 | =item EV_HEAP_CACHE_AT |
|
|
3710 | |
|
|
3711 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3712 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
3713 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3714 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3715 | but avoids random read accesses on heap changes. This improves performance |
|
|
3716 | noticeably with many (hundreds) of watchers. |
|
|
3717 | |
|
|
3718 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3719 | (disabled). |
|
|
3720 | |
|
|
3721 | =item EV_VERIFY |
|
|
3722 | |
|
|
3723 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3724 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3725 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3726 | called. If set to C<2>, then the internal verification code will be |
|
|
3727 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3728 | verification code will be called very frequently, which will slow down |
|
|
3729 | libev considerably. |
|
|
3730 | |
|
|
3731 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3732 | C<0>. |
|
|
3733 | |
2648 | =item EV_COMMON |
3734 | =item EV_COMMON |
2649 | |
3735 | |
2650 | By default, all watchers have a C<void *data> member. By redefining |
3736 | By default, all watchers have a C<void *data> member. By redefining |
2651 | this macro to a something else you can include more and other types of |
3737 | this macro to a something else you can include more and other types of |
2652 | members. You have to define it each time you include one of the files, |
3738 | members. You have to define it each time you include one of the files, |
2653 | though, and it must be identical each time. |
3739 | though, and it must be identical each time. |
2654 | |
3740 | |
2655 | For example, the perl EV module uses something like this: |
3741 | For example, the perl EV module uses something like this: |
2656 | |
3742 | |
2657 | #define EV_COMMON \ |
3743 | #define EV_COMMON \ |
2658 | SV *self; /* contains this struct */ \ |
3744 | SV *self; /* contains this struct */ \ |
2659 | SV *cb_sv, *fh /* note no trailing ";" */ |
3745 | SV *cb_sv, *fh /* note no trailing ";" */ |
2660 | |
3746 | |
2661 | =item EV_CB_DECLARE (type) |
3747 | =item EV_CB_DECLARE (type) |
2662 | |
3748 | |
2663 | =item EV_CB_INVOKE (watcher, revents) |
3749 | =item EV_CB_INVOKE (watcher, revents) |
2664 | |
3750 | |
… | |
… | |
2669 | definition and a statement, respectively. See the F<ev.h> header file for |
3755 | definition and a statement, respectively. See the F<ev.h> header file for |
2670 | their default definitions. One possible use for overriding these is to |
3756 | their default definitions. One possible use for overriding these is to |
2671 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3757 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2672 | method calls instead of plain function calls in C++. |
3758 | method calls instead of plain function calls in C++. |
2673 | |
3759 | |
|
|
3760 | =back |
|
|
3761 | |
2674 | =head2 EXPORTED API SYMBOLS |
3762 | =head2 EXPORTED API SYMBOLS |
2675 | |
3763 | |
2676 | If you need to re-export the API (e.g. via a dll) and you need a list of |
3764 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
2677 | exported symbols, you can use the provided F<Symbol.*> files which list |
3765 | exported symbols, you can use the provided F<Symbol.*> files which list |
2678 | all public symbols, one per line: |
3766 | all public symbols, one per line: |
2679 | |
3767 | |
2680 | Symbols.ev for libev proper |
3768 | Symbols.ev for libev proper |
2681 | Symbols.event for the libevent emulation |
3769 | Symbols.event for the libevent emulation |
2682 | |
3770 | |
2683 | This can also be used to rename all public symbols to avoid clashes with |
3771 | This can also be used to rename all public symbols to avoid clashes with |
2684 | multiple versions of libev linked together (which is obviously bad in |
3772 | multiple versions of libev linked together (which is obviously bad in |
2685 | itself, but sometimes it is inconvinient to avoid this). |
3773 | itself, but sometimes it is inconvenient to avoid this). |
2686 | |
3774 | |
2687 | A sed command like this will create wrapper C<#define>'s that you need to |
3775 | A sed command like this will create wrapper C<#define>'s that you need to |
2688 | include before including F<ev.h>: |
3776 | include before including F<ev.h>: |
2689 | |
3777 | |
2690 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
3778 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
… | |
… | |
2707 | file. |
3795 | file. |
2708 | |
3796 | |
2709 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3797 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
2710 | that everybody includes and which overrides some configure choices: |
3798 | that everybody includes and which overrides some configure choices: |
2711 | |
3799 | |
2712 | #define EV_MINIMAL 1 |
3800 | #define EV_MINIMAL 1 |
2713 | #define EV_USE_POLL 0 |
3801 | #define EV_USE_POLL 0 |
2714 | #define EV_MULTIPLICITY 0 |
3802 | #define EV_MULTIPLICITY 0 |
2715 | #define EV_PERIODIC_ENABLE 0 |
3803 | #define EV_PERIODIC_ENABLE 0 |
2716 | #define EV_STAT_ENABLE 0 |
3804 | #define EV_STAT_ENABLE 0 |
2717 | #define EV_FORK_ENABLE 0 |
3805 | #define EV_FORK_ENABLE 0 |
2718 | #define EV_CONFIG_H <config.h> |
3806 | #define EV_CONFIG_H <config.h> |
2719 | #define EV_MINPRI 0 |
3807 | #define EV_MINPRI 0 |
2720 | #define EV_MAXPRI 0 |
3808 | #define EV_MAXPRI 0 |
2721 | |
3809 | |
2722 | #include "ev++.h" |
3810 | #include "ev++.h" |
2723 | |
3811 | |
2724 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3812 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
2725 | |
3813 | |
2726 | #include "ev_cpp.h" |
3814 | #include "ev_cpp.h" |
2727 | #include "ev.c" |
3815 | #include "ev.c" |
2728 | |
3816 | |
|
|
3817 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
2729 | |
3818 | |
2730 | =head1 COMPLEXITIES |
3819 | =head2 THREADS AND COROUTINES |
2731 | |
3820 | |
2732 | In this section the complexities of (many of) the algorithms used inside |
3821 | =head3 THREADS |
2733 | libev will be explained. For complexity discussions about backends see the |
|
|
2734 | documentation for C<ev_default_init>. |
|
|
2735 | |
3822 | |
2736 | All of the following are about amortised time: If an array needs to be |
3823 | All libev functions are reentrant and thread-safe unless explicitly |
2737 | extended, libev needs to realloc and move the whole array, but this |
3824 | documented otherwise, but libev implements no locking itself. This means |
2738 | happens asymptotically never with higher number of elements, so O(1) might |
3825 | that you can use as many loops as you want in parallel, as long as there |
2739 | mean it might do a lengthy realloc operation in rare cases, but on average |
3826 | are no concurrent calls into any libev function with the same loop |
2740 | it is much faster and asymptotically approaches constant time. |
3827 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3828 | of course): libev guarantees that different event loops share no data |
|
|
3829 | structures that need any locking. |
|
|
3830 | |
|
|
3831 | Or to put it differently: calls with different loop parameters can be done |
|
|
3832 | concurrently from multiple threads, calls with the same loop parameter |
|
|
3833 | must be done serially (but can be done from different threads, as long as |
|
|
3834 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
3835 | a mutex per loop). |
|
|
3836 | |
|
|
3837 | Specifically to support threads (and signal handlers), libev implements |
|
|
3838 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3839 | concurrency on the same event loop, namely waking it up "from the |
|
|
3840 | outside". |
|
|
3841 | |
|
|
3842 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3843 | without or something else still) is best for your problem, then I cannot |
|
|
3844 | help you, but here is some generic advice: |
2741 | |
3845 | |
2742 | =over 4 |
3846 | =over 4 |
2743 | |
3847 | |
2744 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3848 | =item * most applications have a main thread: use the default libev loop |
|
|
3849 | in that thread, or create a separate thread running only the default loop. |
2745 | |
3850 | |
2746 | This means that, when you have a watcher that triggers in one hour and |
3851 | This helps integrating other libraries or software modules that use libev |
2747 | there are 100 watchers that would trigger before that then inserting will |
3852 | themselves and don't care/know about threading. |
2748 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
2749 | |
3853 | |
2750 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3854 | =item * one loop per thread is usually a good model. |
2751 | |
3855 | |
2752 | That means that changing a timer costs less than removing/adding them |
3856 | Doing this is almost never wrong, sometimes a better-performance model |
2753 | as only the relative motion in the event queue has to be paid for. |
3857 | exists, but it is always a good start. |
2754 | |
3858 | |
2755 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3859 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3860 | loop is handed through multiple threads in a kind of round-robin fashion. |
2756 | |
3861 | |
2757 | These just add the watcher into an array or at the head of a list. |
3862 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3863 | better than you currently do :-) |
2758 | |
3864 | |
2759 | =item Stopping check/prepare/idle watchers: O(1) |
3865 | =item * often you need to talk to some other thread which blocks in the |
|
|
3866 | event loop. |
2760 | |
3867 | |
2761 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3868 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
3869 | (or from signal contexts...). |
2762 | |
3870 | |
2763 | These watchers are stored in lists then need to be walked to find the |
3871 | An example use would be to communicate signals or other events that only |
2764 | correct watcher to remove. The lists are usually short (you don't usually |
3872 | work in the default loop by registering the signal watcher with the |
2765 | have many watchers waiting for the same fd or signal). |
3873 | default loop and triggering an C<ev_async> watcher from the default loop |
2766 | |
3874 | watcher callback into the event loop interested in the signal. |
2767 | =item Finding the next timer in each loop iteration: O(1) |
|
|
2768 | |
|
|
2769 | By virtue of using a binary heap, the next timer is always found at the |
|
|
2770 | beginning of the storage array. |
|
|
2771 | |
|
|
2772 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
2773 | |
|
|
2774 | A change means an I/O watcher gets started or stopped, which requires |
|
|
2775 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
2776 | on backend and wether C<ev_io_set> was used). |
|
|
2777 | |
|
|
2778 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
2779 | |
|
|
2780 | =item Priority handling: O(number_of_priorities) |
|
|
2781 | |
|
|
2782 | Priorities are implemented by allocating some space for each |
|
|
2783 | priority. When doing priority-based operations, libev usually has to |
|
|
2784 | linearly search all the priorities, but starting/stopping and activating |
|
|
2785 | watchers becomes O(1) w.r.t. prioritiy handling. |
|
|
2786 | |
3875 | |
2787 | =back |
3876 | =back |
2788 | |
3877 | |
|
|
3878 | =head3 COROUTINES |
2789 | |
3879 | |
2790 | =head1 Win32 platform limitations and workarounds |
3880 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
3881 | libev fully supports nesting calls to its functions from different |
|
|
3882 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3883 | different coroutines, and switch freely between both coroutines running the |
|
|
3884 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3885 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3886 | |
|
|
3887 | Care has been taken to ensure that libev does not keep local state inside |
|
|
3888 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3889 | they do not call any callbacks. |
|
|
3890 | |
|
|
3891 | =head2 COMPILER WARNINGS |
|
|
3892 | |
|
|
3893 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3894 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3895 | scared by this. |
|
|
3896 | |
|
|
3897 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3898 | has different warnings, and each user has different tastes regarding |
|
|
3899 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3900 | targeting a specific compiler and compiler-version. |
|
|
3901 | |
|
|
3902 | Another reason is that some compiler warnings require elaborate |
|
|
3903 | workarounds, or other changes to the code that make it less clear and less |
|
|
3904 | maintainable. |
|
|
3905 | |
|
|
3906 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3907 | wrong (because they don't actually warn about the condition their message |
|
|
3908 | seems to warn about). For example, certain older gcc versions had some |
|
|
3909 | warnings that resulted an extreme number of false positives. These have |
|
|
3910 | been fixed, but some people still insist on making code warn-free with |
|
|
3911 | such buggy versions. |
|
|
3912 | |
|
|
3913 | While libev is written to generate as few warnings as possible, |
|
|
3914 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3915 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3916 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3917 | warnings, not errors, or proof of bugs. |
|
|
3918 | |
|
|
3919 | |
|
|
3920 | =head2 VALGRIND |
|
|
3921 | |
|
|
3922 | Valgrind has a special section here because it is a popular tool that is |
|
|
3923 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
3924 | |
|
|
3925 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3926 | in libev, then check twice: If valgrind reports something like: |
|
|
3927 | |
|
|
3928 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3929 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3930 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3931 | |
|
|
3932 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3933 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
3934 | |
|
|
3935 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3936 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3937 | although an acceptable workaround has been found here), or it might be |
|
|
3938 | confused. |
|
|
3939 | |
|
|
3940 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
3941 | make it into some kind of religion. |
|
|
3942 | |
|
|
3943 | If you are unsure about something, feel free to contact the mailing list |
|
|
3944 | with the full valgrind report and an explanation on why you think this |
|
|
3945 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3946 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3947 | of learning how to interpret valgrind properly. |
|
|
3948 | |
|
|
3949 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3950 | I suggest using suppression lists. |
|
|
3951 | |
|
|
3952 | |
|
|
3953 | =head1 PORTABILITY NOTES |
|
|
3954 | |
|
|
3955 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
2791 | |
3956 | |
2792 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3957 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
2793 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3958 | requires, and its I/O model is fundamentally incompatible with the POSIX |
2794 | model. Libev still offers limited functionality on this platform in |
3959 | model. Libev still offers limited functionality on this platform in |
2795 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3960 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
2796 | descriptors. This only applies when using Win32 natively, not when using |
3961 | descriptors. This only applies when using Win32 natively, not when using |
2797 | e.g. cygwin. |
3962 | e.g. cygwin. |
2798 | |
3963 | |
|
|
3964 | Lifting these limitations would basically require the full |
|
|
3965 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3966 | things, then note that glib does exactly that for you in a very portable |
|
|
3967 | way (note also that glib is the slowest event library known to man). |
|
|
3968 | |
2799 | There is no supported compilation method available on windows except |
3969 | There is no supported compilation method available on windows except |
2800 | embedding it into other applications. |
3970 | embedding it into other applications. |
2801 | |
3971 | |
|
|
3972 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3973 | tries its best, but under most conditions, signals will simply not work. |
|
|
3974 | |
|
|
3975 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3976 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3977 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3978 | so make sure you only write small amounts into your sockets (less than a |
|
|
3979 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
3980 | available). |
|
|
3981 | |
2802 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3982 | Due to the many, low, and arbitrary limits on the win32 platform and |
2803 | abysmal performance of winsockets, using a large number of sockets is not |
3983 | the abysmal performance of winsockets, using a large number of sockets |
2804 | recommended (and not reasonable). If your program needs to use more than |
3984 | is not recommended (and not reasonable). If your program needs to use |
2805 | a hundred or so sockets, then likely it needs to use a totally different |
3985 | more than a hundred or so sockets, then likely it needs to use a totally |
2806 | implementation for windows, as libev offers the POSIX model, which cannot |
3986 | different implementation for windows, as libev offers the POSIX readiness |
2807 | be implemented efficiently on windows (microsoft monopoly games). |
3987 | notification model, which cannot be implemented efficiently on windows |
|
|
3988 | (due to Microsoft monopoly games). |
|
|
3989 | |
|
|
3990 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3991 | section for details) and use the following F<evwrap.h> header file instead |
|
|
3992 | of F<ev.h>: |
|
|
3993 | |
|
|
3994 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3995 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3996 | |
|
|
3997 | #include "ev.h" |
|
|
3998 | |
|
|
3999 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
4000 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
4001 | |
|
|
4002 | #include "evwrap.h" |
|
|
4003 | #include "ev.c" |
2808 | |
4004 | |
2809 | =over 4 |
4005 | =over 4 |
2810 | |
4006 | |
2811 | =item The winsocket select function |
4007 | =item The winsocket select function |
2812 | |
4008 | |
2813 | The winsocket C<select> function doesn't follow POSIX in that it requires |
4009 | The winsocket C<select> function doesn't follow POSIX in that it |
2814 | socket I<handles> and not socket I<file descriptors>. This makes select |
4010 | requires socket I<handles> and not socket I<file descriptors> (it is |
2815 | very inefficient, and also requires a mapping from file descriptors |
4011 | also extremely buggy). This makes select very inefficient, and also |
2816 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
4012 | requires a mapping from file descriptors to socket handles (the Microsoft |
2817 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
4013 | C runtime provides the function C<_open_osfhandle> for this). See the |
2818 | symbols for more info. |
4014 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
4015 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
2819 | |
4016 | |
2820 | The configuration for a "naked" win32 using the microsoft runtime |
4017 | The configuration for a "naked" win32 using the Microsoft runtime |
2821 | libraries and raw winsocket select is: |
4018 | libraries and raw winsocket select is: |
2822 | |
4019 | |
2823 | #define EV_USE_SELECT 1 |
4020 | #define EV_USE_SELECT 1 |
2824 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4021 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
2825 | |
4022 | |
2826 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4023 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
2827 | complexity in the O(n²) range when using win32. |
4024 | complexity in the O(n²) range when using win32. |
2828 | |
4025 | |
2829 | =item Limited number of file descriptors |
4026 | =item Limited number of file descriptors |
2830 | |
4027 | |
2831 | Windows has numerous arbitrary (and low) limits on things. Early versions |
4028 | Windows has numerous arbitrary (and low) limits on things. |
2832 | of winsocket's select only supported waiting for a max. of C<64> handles |
4029 | |
|
|
4030 | Early versions of winsocket's select only supported waiting for a maximum |
2833 | (probably owning to the fact that all windows kernels can only wait for |
4031 | of C<64> handles (probably owning to the fact that all windows kernels |
2834 | C<64> things at the same time internally; microsoft recommends spawning a |
4032 | can only wait for C<64> things at the same time internally; Microsoft |
2835 | chain of threads and wait for 63 handles and the previous thread in each). |
4033 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4034 | previous thread in each. Sounds great!). |
2836 | |
4035 | |
2837 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4036 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
2838 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4037 | to some high number (e.g. C<2048>) before compiling the winsocket select |
2839 | call (which might be in libev or elsewhere, for example, perl does its own |
4038 | call (which might be in libev or elsewhere, for example, perl and many |
2840 | select emulation on windows). |
4039 | other interpreters do their own select emulation on windows). |
2841 | |
4040 | |
2842 | Another limit is the number of file descriptors in the microsoft runtime |
4041 | Another limit is the number of file descriptors in the Microsoft runtime |
2843 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4042 | libraries, which by default is C<64> (there must be a hidden I<64> |
2844 | or something like this inside microsoft). You can increase this by calling |
4043 | fetish or something like this inside Microsoft). You can increase this |
2845 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4044 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
2846 | arbitrary limit), but is broken in many versions of the microsoft runtime |
4045 | (another arbitrary limit), but is broken in many versions of the Microsoft |
2847 | libraries. |
|
|
2848 | |
|
|
2849 | This might get you to about C<512> or C<2048> sockets (depending on |
4046 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
2850 | windows version and/or the phase of the moon). To get more, you need to |
4047 | (depending on windows version and/or the phase of the moon). To get more, |
2851 | wrap all I/O functions and provide your own fd management, but the cost of |
4048 | you need to wrap all I/O functions and provide your own fd management, but |
2852 | calling select (O(n²)) will likely make this unworkable. |
4049 | the cost of calling select (O(n²)) will likely make this unworkable. |
2853 | |
4050 | |
2854 | =back |
4051 | =back |
2855 | |
4052 | |
|
|
4053 | =head2 PORTABILITY REQUIREMENTS |
|
|
4054 | |
|
|
4055 | In addition to a working ISO-C implementation and of course the |
|
|
4056 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4057 | |
|
|
4058 | =over 4 |
|
|
4059 | |
|
|
4060 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
4061 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
4062 | |
|
|
4063 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4064 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
4065 | assumes that the same (machine) code can be used to call any watcher |
|
|
4066 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4067 | calls them using an C<ev_watcher *> internally. |
|
|
4068 | |
|
|
4069 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
4070 | |
|
|
4071 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
4072 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
4073 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
4074 | believed to be sufficiently portable. |
|
|
4075 | |
|
|
4076 | =item C<sigprocmask> must work in a threaded environment |
|
|
4077 | |
|
|
4078 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
4079 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
4080 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
4081 | thread" or will block signals process-wide, both behaviours would |
|
|
4082 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
4083 | C<pthread_sigmask> could complicate things, however. |
|
|
4084 | |
|
|
4085 | The most portable way to handle signals is to block signals in all threads |
|
|
4086 | except the initial one, and run the default loop in the initial thread as |
|
|
4087 | well. |
|
|
4088 | |
|
|
4089 | =item C<long> must be large enough for common memory allocation sizes |
|
|
4090 | |
|
|
4091 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
4092 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
4093 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4094 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
4095 | watchers. |
|
|
4096 | |
|
|
4097 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
4098 | |
|
|
4099 | The type C<double> is used to represent timestamps. It is required to |
|
|
4100 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4101 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4102 | implementations implementing IEEE 754, which is basically all existing |
|
|
4103 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4104 | 2200. |
|
|
4105 | |
|
|
4106 | =back |
|
|
4107 | |
|
|
4108 | If you know of other additional requirements drop me a note. |
|
|
4109 | |
|
|
4110 | |
|
|
4111 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
4112 | |
|
|
4113 | In this section the complexities of (many of) the algorithms used inside |
|
|
4114 | libev will be documented. For complexity discussions about backends see |
|
|
4115 | the documentation for C<ev_default_init>. |
|
|
4116 | |
|
|
4117 | All of the following are about amortised time: If an array needs to be |
|
|
4118 | extended, libev needs to realloc and move the whole array, but this |
|
|
4119 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
4120 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4121 | average it is much faster and asymptotically approaches constant time. |
|
|
4122 | |
|
|
4123 | =over 4 |
|
|
4124 | |
|
|
4125 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
4126 | |
|
|
4127 | This means that, when you have a watcher that triggers in one hour and |
|
|
4128 | there are 100 watchers that would trigger before that, then inserting will |
|
|
4129 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
4130 | |
|
|
4131 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
4132 | |
|
|
4133 | That means that changing a timer costs less than removing/adding them, |
|
|
4134 | as only the relative motion in the event queue has to be paid for. |
|
|
4135 | |
|
|
4136 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
4137 | |
|
|
4138 | These just add the watcher into an array or at the head of a list. |
|
|
4139 | |
|
|
4140 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
4141 | |
|
|
4142 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
4143 | |
|
|
4144 | These watchers are stored in lists, so they need to be walked to find the |
|
|
4145 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
4146 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4147 | is rare). |
|
|
4148 | |
|
|
4149 | =item Finding the next timer in each loop iteration: O(1) |
|
|
4150 | |
|
|
4151 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4152 | fixed position in the storage array. |
|
|
4153 | |
|
|
4154 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4155 | |
|
|
4156 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4157 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4158 | on backend and whether C<ev_io_set> was used). |
|
|
4159 | |
|
|
4160 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4161 | |
|
|
4162 | =item Priority handling: O(number_of_priorities) |
|
|
4163 | |
|
|
4164 | Priorities are implemented by allocating some space for each |
|
|
4165 | priority. When doing priority-based operations, libev usually has to |
|
|
4166 | linearly search all the priorities, but starting/stopping and activating |
|
|
4167 | watchers becomes O(1) with respect to priority handling. |
|
|
4168 | |
|
|
4169 | =item Sending an ev_async: O(1) |
|
|
4170 | |
|
|
4171 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4172 | |
|
|
4173 | =item Processing signals: O(max_signal_number) |
|
|
4174 | |
|
|
4175 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4176 | calls in the current loop iteration. Checking for async and signal events |
|
|
4177 | involves iterating over all running async watchers or all signal numbers. |
|
|
4178 | |
|
|
4179 | =back |
|
|
4180 | |
|
|
4181 | |
|
|
4182 | =head1 GLOSSARY |
|
|
4183 | |
|
|
4184 | =over 4 |
|
|
4185 | |
|
|
4186 | =item active |
|
|
4187 | |
|
|
4188 | A watcher is active as long as it has been started (has been attached to |
|
|
4189 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4190 | |
|
|
4191 | =item application |
|
|
4192 | |
|
|
4193 | In this document, an application is whatever is using libev. |
|
|
4194 | |
|
|
4195 | =item callback |
|
|
4196 | |
|
|
4197 | The address of a function that is called when some event has been |
|
|
4198 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4199 | received the event, and the actual event bitset. |
|
|
4200 | |
|
|
4201 | =item callback invocation |
|
|
4202 | |
|
|
4203 | The act of calling the callback associated with a watcher. |
|
|
4204 | |
|
|
4205 | =item event |
|
|
4206 | |
|
|
4207 | A change of state of some external event, such as data now being available |
|
|
4208 | for reading on a file descriptor, time having passed or simply not having |
|
|
4209 | any other events happening anymore. |
|
|
4210 | |
|
|
4211 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4212 | C<EV_TIMEOUT>). |
|
|
4213 | |
|
|
4214 | =item event library |
|
|
4215 | |
|
|
4216 | A software package implementing an event model and loop. |
|
|
4217 | |
|
|
4218 | =item event loop |
|
|
4219 | |
|
|
4220 | An entity that handles and processes external events and converts them |
|
|
4221 | into callback invocations. |
|
|
4222 | |
|
|
4223 | =item event model |
|
|
4224 | |
|
|
4225 | The model used to describe how an event loop handles and processes |
|
|
4226 | watchers and events. |
|
|
4227 | |
|
|
4228 | =item pending |
|
|
4229 | |
|
|
4230 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4231 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4232 | pending status is explicitly cleared by the application. |
|
|
4233 | |
|
|
4234 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4235 | its pending status. |
|
|
4236 | |
|
|
4237 | =item real time |
|
|
4238 | |
|
|
4239 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4240 | |
|
|
4241 | =item wall-clock time |
|
|
4242 | |
|
|
4243 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4244 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4245 | clock. |
|
|
4246 | |
|
|
4247 | =item watcher |
|
|
4248 | |
|
|
4249 | A data structure that describes interest in certain events. Watchers need |
|
|
4250 | to be started (attached to an event loop) before they can receive events. |
|
|
4251 | |
|
|
4252 | =item watcher invocation |
|
|
4253 | |
|
|
4254 | The act of calling the callback associated with a watcher. |
|
|
4255 | |
|
|
4256 | =back |
2856 | |
4257 | |
2857 | =head1 AUTHOR |
4258 | =head1 AUTHOR |
2858 | |
4259 | |
2859 | Marc Lehmann <libev@schmorp.de>. |
4260 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
2860 | |
4261 | |