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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
52 | |
54 | |
53 | // initialise a timer watcher, then start it |
55 | // initialise a timer watcher, then start it |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // break was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familiarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
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90 | |
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91 | =head1 ABOUT LIBEV |
70 | |
92 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
95 | these event sources and provide your program with events. |
74 | |
96 | |
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84 | =head2 FEATURES |
106 | =head2 FEATURES |
85 | |
107 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
115 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
117 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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118 | limited support for fork events (C<ev_fork>). |
96 | |
119 | |
97 | It also is quite fast (see this |
120 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
121 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
122 | for example). |
100 | |
123 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
132 | this argument. |
110 | |
133 | |
111 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
112 | |
135 | |
113 | Libev represents time as a single floating point number, representing the |
136 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
138 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
141 | any calculations on it, you should treat it as some floating point value. |
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142 | |
119 | component C<stamp> might indicate, it is also used for time differences |
143 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
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145 | |
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146 | =head1 ERROR HANDLING |
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147 | |
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148 | Libev knows three classes of errors: operating system errors, usage errors |
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149 | and internal errors (bugs). |
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150 | |
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151 | When libev catches an operating system error it cannot handle (for example |
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152 | a system call indicating a condition libev cannot fix), it calls the callback |
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153 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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154 | abort. The default is to print a diagnostic message and to call C<abort |
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155 | ()>. |
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156 | |
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157 | When libev detects a usage error such as a negative timer interval, then |
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158 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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159 | so C<NDEBUG> will disable this checking): these are programming errors in |
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160 | the libev caller and need to be fixed there. |
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161 | |
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162 | Libev also has a few internal error-checking C<assert>ions, and also has |
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163 | extensive consistency checking code. These do not trigger under normal |
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164 | circumstances, as they indicate either a bug in libev or worse. |
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165 | |
121 | |
166 | |
122 | =head1 GLOBAL FUNCTIONS |
167 | =head1 GLOBAL FUNCTIONS |
123 | |
168 | |
124 | These functions can be called anytime, even before initialising the |
169 | These functions can be called anytime, even before initialising the |
125 | library in any way. |
170 | library in any way. |
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128 | |
173 | |
129 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
130 | |
175 | |
131 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
132 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
133 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_now_update> and C<ev_now>. |
134 | |
180 | |
135 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
136 | |
182 | |
137 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
138 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
139 | this is a subsecond-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
140 | |
192 | |
141 | =item int ev_version_major () |
193 | =item int ev_version_major () |
142 | |
194 | |
143 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
144 | |
196 | |
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155 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
156 | compatible to older versions, so a larger minor version alone is usually |
208 | compatible to older versions, so a larger minor version alone is usually |
157 | not a problem. |
209 | not a problem. |
158 | |
210 | |
159 | Example: Make sure we haven't accidentally been linked against the wrong |
211 | Example: Make sure we haven't accidentally been linked against the wrong |
160 | version. |
212 | version (note, however, that this will not detect other ABI mismatches, |
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213 | such as LFS or reentrancy). |
161 | |
214 | |
162 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
163 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
164 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
165 | |
218 | |
166 | =item unsigned int ev_supported_backends () |
219 | =item unsigned int ev_supported_backends () |
167 | |
220 | |
168 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
221 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
169 | value) compiled into this binary of libev (independent of their |
222 | value) compiled into this binary of libev (independent of their |
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171 | a description of the set values. |
224 | a description of the set values. |
172 | |
225 | |
173 | Example: make sure we have the epoll method, because yeah this is cool and |
226 | Example: make sure we have the epoll method, because yeah this is cool and |
174 | a must have and can we have a torrent of it please!!!11 |
227 | a must have and can we have a torrent of it please!!!11 |
175 | |
228 | |
176 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
177 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
178 | |
231 | |
179 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
180 | |
233 | |
181 | Return the set of all backends compiled into this binary of libev and also |
234 | Return the set of all backends compiled into this binary of libev and |
182 | recommended for this platform. This set is often smaller than the one |
235 | also recommended for this platform, meaning it will work for most file |
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236 | descriptor types. This set is often smaller than the one returned by |
183 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
237 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
184 | most BSDs and will not be autodetected unless you explicitly request it |
238 | and will not be auto-detected unless you explicitly request it (assuming |
185 | (assuming you know what you are doing). This is the set of backends that |
239 | you know what you are doing). This is the set of backends that libev will |
186 | libev will probe for if you specify no backends explicitly. |
240 | probe for if you specify no backends explicitly. |
187 | |
241 | |
188 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
189 | |
243 | |
190 | Returns the set of backends that are embeddable in other event loops. This |
244 | Returns the set of backends that are embeddable in other event loops. This |
191 | is the theoretical, all-platform, value. To find which backends |
245 | value is platform-specific but can include backends not available on the |
192 | might be supported on the current system, you would need to look at |
246 | current system. To find which embeddable backends might be supported on |
193 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
194 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
195 | |
249 | |
196 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
197 | |
251 | |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
199 | |
253 | |
200 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
201 | semantics is identical - to the realloc C function). It is used to |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
202 | allocate and free memory (no surprises here). If it returns zero when |
256 | used to allocate and free memory (no surprises here). If it returns zero |
203 | memory needs to be allocated, the library might abort or take some |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
204 | potentially destructive action. The default is your system realloc |
258 | or take some potentially destructive action. |
205 | function. |
259 | |
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260 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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261 | correct C<realloc> semantics, libev will use a wrapper around the system |
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262 | C<realloc> and C<free> functions by default. |
206 | |
263 | |
207 | You could override this function in high-availability programs to, say, |
264 | You could override this function in high-availability programs to, say, |
208 | free some memory if it cannot allocate memory, to use a special allocator, |
265 | free some memory if it cannot allocate memory, to use a special allocator, |
209 | or even to sleep a while and retry until some memory is available. |
266 | or even to sleep a while and retry until some memory is available. |
210 | |
267 | |
211 | Example: Replace the libev allocator with one that waits a bit and then |
268 | Example: Replace the libev allocator with one that waits a bit and then |
212 | retries). |
269 | retries (example requires a standards-compliant C<realloc>). |
213 | |
270 | |
214 | static void * |
271 | static void * |
215 | persistent_realloc (void *ptr, size_t size) |
272 | persistent_realloc (void *ptr, size_t size) |
216 | { |
273 | { |
217 | for (;;) |
274 | for (;;) |
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226 | } |
283 | } |
227 | |
284 | |
228 | ... |
285 | ... |
229 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
230 | |
287 | |
231 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
232 | |
289 | |
233 | Set the callback function to call on a retryable syscall error (such |
290 | Set the callback function to call on a retryable system call error (such |
234 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
235 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
236 | callback is set, then libev will expect it to remedy the sitution, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
237 | matter what, when it returns. That is, libev will generally retry the |
294 | matter what, when it returns. That is, libev will generally retry the |
238 | requested operation, or, if the condition doesn't go away, do bad stuff |
295 | requested operation, or, if the condition doesn't go away, do bad stuff |
239 | (such as abort). |
296 | (such as abort). |
240 | |
297 | |
241 | Example: This is basically the same thing that libev does internally, too. |
298 | Example: This is basically the same thing that libev does internally, too. |
… | |
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248 | } |
305 | } |
249 | |
306 | |
250 | ... |
307 | ... |
251 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
252 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
253 | =back |
323 | =back |
254 | |
324 | |
255 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
256 | |
326 | |
257 | An event loop is described by a C<struct ev_loop *>. The library knows two |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
258 | types of such loops, the I<default> loop, which supports signals and child |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
259 | events, and dynamically created loops which do not. |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
260 | |
330 | |
261 | If you use threads, a common model is to run the default event loop |
331 | The library knows two types of such loops, the I<default> loop, which |
262 | in your main thread (or in a separate thread) and for each thread you |
332 | supports child process events, and dynamically created event loops which |
263 | create, you also create another event loop. Libev itself does no locking |
333 | do not. |
264 | whatsoever, so if you mix calls to the same event loop in different |
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265 | threads, make sure you lock (this is usually a bad idea, though, even if |
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266 | done correctly, because it's hideous and inefficient). |
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267 | |
334 | |
268 | =over 4 |
335 | =over 4 |
269 | |
336 | |
270 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
271 | |
338 | |
272 | This will initialise the default event loop if it hasn't been initialised |
339 | This returns the "default" event loop object, which is what you should |
273 | yet and return it. If the default loop could not be initialised, returns |
340 | normally use when you just need "the event loop". Event loop objects and |
274 | false. If it already was initialised it simply returns it (and ignores the |
341 | the C<flags> parameter are described in more detail in the entry for |
275 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
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343 | |
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344 | If the default loop is already initialised then this function simply |
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345 | returns it (and ignores the flags. If that is troubling you, check |
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346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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347 | flags, which should almost always be C<0>, unless the caller is also the |
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348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
276 | |
349 | |
277 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
278 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
279 | |
352 | |
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353 | Note that this function is I<not> thread-safe, so if you want to use it |
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354 | from multiple threads, you have to employ some kind of mutex (note also |
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355 | that this case is unlikely, as loops cannot be shared easily between |
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356 | threads anyway). |
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357 | |
280 | The default loop is the only loop that can handle C<ev_signal> and |
358 | The default loop is the only loop that can handle C<ev_child> watchers, |
281 | C<ev_child> watchers, and to do this, it always registers a handler |
359 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
282 | for C<SIGCHLD>. If this is a problem for your app you can either |
360 | a problem for your application you can either create a dynamic loop with |
283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
361 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
284 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
285 | C<ev_default_init>. |
363 | |
|
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364 | Example: This is the most typical usage. |
|
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365 | |
|
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366 | if (!ev_default_loop (0)) |
|
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367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
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368 | |
|
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369 | Example: Restrict libev to the select and poll backends, and do not allow |
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370 | environment settings to be taken into account: |
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371 | |
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372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
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373 | |
|
|
374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
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375 | |
|
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376 | This will create and initialise a new event loop object. If the loop |
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377 | could not be initialised, returns false. |
|
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378 | |
|
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379 | This function is thread-safe, and one common way to use libev with |
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380 | threads is indeed to create one loop per thread, and using the default |
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381 | loop in the "main" or "initial" thread. |
286 | |
382 | |
287 | The flags argument can be used to specify special behaviour or specific |
383 | The flags argument can be used to specify special behaviour or specific |
288 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
289 | |
385 | |
290 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
296 | The default flags value. Use this if you have no clue (it's the right |
392 | The default flags value. Use this if you have no clue (it's the right |
297 | thing, believe me). |
393 | thing, believe me). |
298 | |
394 | |
299 | =item C<EVFLAG_NOENV> |
395 | =item C<EVFLAG_NOENV> |
300 | |
396 | |
301 | If this flag bit is ored into the flag value (or the program runs setuid |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
302 | or setgid) then libev will I<not> look at the environment variable |
398 | or setgid) then libev will I<not> look at the environment variable |
303 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
304 | override the flags completely if it is found in the environment. This is |
400 | override the flags completely if it is found in the environment. This is |
305 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, or to work |
306 | around bugs. |
402 | around bugs. |
307 | |
403 | |
308 | =item C<EVFLAG_FORKCHECK> |
404 | =item C<EVFLAG_FORKCHECK> |
309 | |
405 | |
310 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
311 | a fork, you can also make libev check for a fork in each iteration by |
407 | make libev check for a fork in each iteration by enabling this flag. |
312 | enabling this flag. |
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313 | |
408 | |
314 | This works by calling C<getpid ()> on every iteration of the loop, |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
315 | and thus this might slow down your event loop if you do a lot of loop |
410 | and thus this might slow down your event loop if you do a lot of loop |
316 | iterations and little real work, but is usually not noticeable (on my |
411 | iterations and little real work, but is usually not noticeable (on my |
317 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
318 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
319 | C<pthread_atfork> which is even faster). |
414 | C<pthread_atfork> which is even faster). |
320 | |
415 | |
321 | The big advantage of this flag is that you can forget about fork (and |
416 | The big advantage of this flag is that you can forget about fork (and |
322 | forget about forgetting to tell libev about forking) when you use this |
417 | forget about forgetting to tell libev about forking) when you use this |
323 | flag. |
418 | flag. |
324 | |
419 | |
325 | This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
326 | environment variable. |
421 | environment variable. |
|
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422 | |
|
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423 | =item C<EVFLAG_NOINOTIFY> |
|
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424 | |
|
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425 | When this flag is specified, then libev will not attempt to use the |
|
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426 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
|
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427 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
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428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
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429 | |
|
|
430 | =item C<EVFLAG_SIGNALFD> |
|
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431 | |
|
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432 | When this flag is specified, then libev will attempt to use the |
|
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433 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
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434 | delivers signals synchronously, which makes it both faster and might make |
|
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435 | it possible to get the queued signal data. It can also simplify signal |
|
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436 | handling with threads, as long as you properly block signals in your |
|
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437 | threads that are not interested in handling them. |
|
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438 | |
|
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439 | Signalfd will not be used by default as this changes your signal mask, and |
|
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440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
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441 | example) that can't properly initialise their signal masks. |
|
|
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
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444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
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446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
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447 | when you want to receive them. |
|
|
448 | |
|
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449 | This behaviour is useful when you want to do your own signal handling, or |
|
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450 | want to handle signals only in specific threads and want to avoid libev |
|
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451 | unblocking the signals. |
|
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452 | |
|
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453 | It's also required by POSIX in a threaded program, as libev calls |
|
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454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
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455 | |
|
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456 | This flag's behaviour will become the default in future versions of libev. |
327 | |
457 | |
328 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
329 | |
459 | |
330 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
331 | libev tries to roll its own fd_set with no limits on the number of fds, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
332 | but if that fails, expect a fairly low limit on the number of fds when |
462 | but if that fails, expect a fairly low limit on the number of fds when |
333 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
463 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
334 | usually the fastest backend for a low number of (low-numbered :) fds. |
464 | usually the fastest backend for a low number of (low-numbered :) fds. |
335 | |
465 | |
336 | To get good performance out of this backend you need a high amount of |
466 | To get good performance out of this backend you need a high amount of |
337 | parallelity (most of the file descriptors should be busy). If you are |
467 | parallelism (most of the file descriptors should be busy). If you are |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
468 | writing a server, you should C<accept ()> in a loop to accept as many |
339 | connections as possible during one iteration. You might also want to have |
469 | connections as possible during one iteration. You might also want to have |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
470 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
341 | readyness notifications you get per iteration. |
471 | readiness notifications you get per iteration. |
|
|
472 | |
|
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473 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
474 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
475 | C<exceptfds> set on that platform). |
342 | |
476 | |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
477 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
344 | |
478 | |
345 | And this is your standard poll(2) backend. It's more complicated |
479 | And this is your standard poll(2) backend. It's more complicated |
346 | than select, but handles sparse fds better and has no artificial |
480 | than select, but handles sparse fds better and has no artificial |
347 | limit on the number of fds you can use (except it will slow down |
481 | limit on the number of fds you can use (except it will slow down |
348 | considerably with a lot of inactive fds). It scales similarly to select, |
482 | considerably with a lot of inactive fds). It scales similarly to select, |
349 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
483 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
350 | performance tips. |
484 | performance tips. |
351 | |
485 | |
|
|
486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
488 | |
352 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
353 | |
490 | |
|
|
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
492 | kernels). |
|
|
493 | |
354 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
355 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
356 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
357 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
497 | fd), epoll scales either O(1) or O(active_fds). |
358 | of shortcomings, such as silently dropping events in some hard-to-detect |
498 | |
359 | cases and rewiring a syscall per fd change, no fork support and bad |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
360 | support for dup. |
500 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
501 | dropping file descriptors, requiring a system call per change per file |
|
|
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
|
|
506 | forks then I<both> parent and child process have to recreate the epoll |
|
|
507 | set, which can take considerable time (one syscall per file descriptor) |
|
|
508 | and is of course hard to detect. |
|
|
509 | |
|
|
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
|
|
511 | but of course I<doesn't>, and epoll just loves to report events for |
|
|
512 | totally I<different> file descriptors (even already closed ones, so |
|
|
513 | one cannot even remove them from the set) than registered in the set |
|
|
514 | (especially on SMP systems). Libev tries to counter these spurious |
|
|
515 | notifications by employing an additional generation counter and comparing |
|
|
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
520 | not least, it also refuses to work with some file descriptors which work |
|
|
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
522 | |
|
|
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
361 | |
526 | |
362 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
363 | will result in some caching, there is still a syscall per such incident |
528 | will result in some caching, there is still a system call per such |
364 | (because the fd could point to a different file description now), so its |
529 | incident (because the same I<file descriptor> could point to a different |
365 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
366 | very well if you register events for both fds. |
531 | file descriptors might not work very well if you register events for both |
367 | |
532 | file descriptors. |
368 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
369 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
370 | (or space) is available. |
|
|
371 | |
533 | |
372 | Best performance from this backend is achieved by not unregistering all |
534 | Best performance from this backend is achieved by not unregistering all |
373 | watchers for a file descriptor until it has been closed, if possible, i.e. |
535 | watchers for a file descriptor until it has been closed, if possible, |
374 | keep at least one watcher active per fd at all times. |
536 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
537 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
538 | extra overhead. A fork can both result in spurious notifications as well |
|
|
539 | as in libev having to destroy and recreate the epoll object, which can |
|
|
540 | take considerable time and thus should be avoided. |
375 | |
541 | |
|
|
542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
543 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
544 | the usage. So sad. |
|
|
545 | |
376 | While nominally embeddeble in other event loops, this feature is broken in |
546 | While nominally embeddable in other event loops, this feature is broken in |
377 | all kernel versions tested so far. |
547 | all kernel versions tested so far. |
|
|
548 | |
|
|
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
550 | C<EVBACKEND_POLL>. |
378 | |
551 | |
379 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
380 | |
553 | |
381 | Kqueue deserves special mention, as at the time of this writing, it |
554 | Kqueue deserves special mention, as at the time of this writing, it |
382 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
555 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
383 | with anything but sockets and pipes, except on Darwin, where of course |
556 | with anything but sockets and pipes, except on Darwin, where of course |
384 | it's completely useless). For this reason it's not being "autodetected" |
557 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
558 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
559 | without API changes to existing programs. For this reason it's not being |
385 | unless you explicitly specify it explicitly in the flags (i.e. using |
560 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
386 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
561 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
387 | system like NetBSD. |
562 | system like NetBSD. |
388 | |
563 | |
389 | You still can embed kqueue into a normal poll or select backend and use it |
564 | You still can embed kqueue into a normal poll or select backend and use it |
390 | only for sockets (after having made sure that sockets work with kqueue on |
565 | only for sockets (after having made sure that sockets work with kqueue on |
391 | the target platform). See C<ev_embed> watchers for more info. |
566 | the target platform). See C<ev_embed> watchers for more info. |
392 | |
567 | |
393 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
394 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
395 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
396 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
397 | two event changes per incident, support for C<fork ()> is very bad and it |
572 | two event changes per incident. Support for C<fork ()> is very bad (but |
398 | drops fds silently in similarly hard-to-detect cases. |
573 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
574 | cases |
399 | |
575 | |
400 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
401 | |
577 | |
402 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
403 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
404 | almost everywhere, you should only use it when you have a lot of sockets |
580 | almost everywhere, you should only use it when you have a lot of sockets |
405 | (for which it usually works), by embedding it into another event loop |
581 | (for which it usually works), by embedding it into another event loop |
406 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
582 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
407 | sockets. |
583 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
584 | |
|
|
585 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
586 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
587 | C<NOTE_EOF>. |
408 | |
588 | |
409 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
589 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
410 | |
590 | |
411 | This is not implemented yet (and might never be, unless you send me an |
591 | This is not implemented yet (and might never be, unless you send me an |
412 | implementation). According to reports, C</dev/poll> only supports sockets |
592 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
416 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
417 | |
597 | |
418 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
419 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
420 | |
600 | |
421 | Please note that solaris event ports can deliver a lot of spurious |
|
|
422 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
423 | blocking when no data (or space) is available. |
|
|
424 | |
|
|
425 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
426 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
428 | might perform better. |
604 | might perform better. |
429 | |
605 | |
430 | On the positive side, ignoring the spurious readyness notifications, this |
606 | On the positive side, this backend actually performed fully to |
431 | backend actually performed to specification in all tests and is fully |
607 | specification in all tests and is fully embeddable, which is a rare feat |
432 | embeddable, which is a rare feat among the OS-specific backends. |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
|
|
620 | |
|
|
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
622 | C<EVBACKEND_POLL>. |
433 | |
623 | |
434 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
435 | |
625 | |
436 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
437 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
438 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
439 | |
629 | |
440 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
441 | |
639 | |
442 | =back |
640 | =back |
443 | |
641 | |
444 | If one or more of these are ored into the flags value, then only these |
642 | If one or more of the backend flags are or'ed into the flags value, |
445 | backends will be tried (in the reverse order as listed here). If none are |
643 | then only these backends will be tried (in the reverse order as listed |
446 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
447 | |
645 | ()> will be tried. |
448 | The most typical usage is like this: |
|
|
449 | |
|
|
450 | if (!ev_default_loop (0)) |
|
|
451 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
452 | |
|
|
453 | Restrict libev to the select and poll backends, and do not allow |
|
|
454 | environment settings to be taken into account: |
|
|
455 | |
|
|
456 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
457 | |
|
|
458 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
459 | available (warning, breaks stuff, best use only with your own private |
|
|
460 | event loop and only if you know the OS supports your types of fds): |
|
|
461 | |
|
|
462 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
463 | |
|
|
464 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
465 | |
|
|
466 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
467 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
468 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
470 | |
646 | |
471 | Example: Try to create a event loop that uses epoll and nothing else. |
647 | Example: Try to create a event loop that uses epoll and nothing else. |
472 | |
648 | |
473 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
474 | if (!epoller) |
650 | if (!epoller) |
475 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
476 | |
652 | |
|
|
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
654 | used if available. |
|
|
655 | |
|
|
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
657 | |
477 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
478 | |
659 | |
479 | Destroys the default loop again (frees all memory and kernel state |
660 | Destroys an event loop object (frees all memory and kernel state |
480 | etc.). None of the active event watchers will be stopped in the normal |
661 | etc.). None of the active event watchers will be stopped in the normal |
481 | sense, so e.g. C<ev_is_active> might still return true. It is your |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
482 | responsibility to either stop all watchers cleanly yoursef I<before> |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
483 | calling this function, or cope with the fact afterwards (which is usually |
664 | calling this function, or cope with the fact afterwards (which is usually |
484 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
665 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
485 | for example). |
666 | for example). |
486 | |
667 | |
487 | Note that certain global state, such as signal state, will not be freed by |
668 | Note that certain global state, such as signal state (and installed signal |
488 | this function, and related watchers (such as signal and child watchers) |
669 | handlers), will not be freed by this function, and related watchers (such |
489 | would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
490 | |
671 | |
491 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
492 | rare occasion where you really need to free e.g. the signal handling |
673 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
674 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
675 | |
|
|
676 | Note that it is not advisable to call this function on the default loop |
|
|
677 | except in the rare occasion where you really need to free its resources. |
493 | pipe fds. If you need dynamically allocated loops it is better to use |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
494 | C<ev_loop_new> and C<ev_loop_destroy>). |
679 | and C<ev_loop_destroy>. |
495 | |
680 | |
496 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
497 | |
682 | |
498 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
499 | earlier call to C<ev_loop_new>. |
|
|
500 | |
|
|
501 | =item ev_default_fork () |
|
|
502 | |
|
|
503 | This function sets a flag that causes subsequent C<ev_loop> iterations |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
504 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
505 | name, you can call it anytime, but it makes most sense after forking, in |
685 | name, you can call it anytime, but it makes most sense after forking, in |
506 | the child process (or both child and parent, but that again makes little |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
507 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
508 | functions, and it will only take effect at the next C<ev_loop> iteration. |
688 | |
|
|
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
692 | during fork. |
509 | |
693 | |
510 | On the other hand, you only need to call this function in the child |
694 | On the other hand, you only need to call this function in the child |
511 | process if and only if you want to use the event library in the child. If |
695 | process if and only if you want to use the event loop in the child. If |
512 | you just fork+exec, you don't have to call it at all. |
696 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
697 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
698 | difference, but libev will usually detect this case on its own and do a |
|
|
699 | costly reset of the backend). |
513 | |
700 | |
514 | The function itself is quite fast and it's usually not a problem to call |
701 | The function itself is quite fast and it's usually not a problem to call |
515 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
516 | quite nicely into a call to C<pthread_atfork>: |
|
|
517 | |
703 | |
|
|
704 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
705 | using pthreads. |
|
|
706 | |
|
|
707 | static void |
|
|
708 | post_fork_child (void) |
|
|
709 | { |
|
|
710 | ev_loop_fork (EV_DEFAULT); |
|
|
711 | } |
|
|
712 | |
|
|
713 | ... |
518 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
519 | |
|
|
520 | =item ev_loop_fork (loop) |
|
|
521 | |
|
|
522 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
523 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
524 | after fork, and how you do this is entirely your own problem. |
|
|
525 | |
715 | |
526 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
527 | |
717 | |
528 | Returns true when the given loop actually is the default loop, false otherwise. |
718 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
719 | otherwise. |
529 | |
720 | |
530 | =item unsigned int ev_loop_count (loop) |
721 | =item unsigned int ev_iteration (loop) |
531 | |
722 | |
532 | Returns the count of loop iterations for the loop, which is identical to |
723 | Returns the current iteration count for the event loop, which is identical |
533 | the number of times libev did poll for new events. It starts at C<0> and |
724 | to the number of times libev did poll for new events. It starts at C<0> |
534 | happily wraps around with enough iterations. |
725 | and happily wraps around with enough iterations. |
535 | |
726 | |
536 | This value can sometimes be useful as a generation counter of sorts (it |
727 | This value can sometimes be useful as a generation counter of sorts (it |
537 | "ticks" the number of loop iterations), as it roughly corresponds with |
728 | "ticks" the number of loop iterations), as it roughly corresponds with |
538 | C<ev_prepare> and C<ev_check> calls. |
729 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
730 | prepare and check phases. |
|
|
731 | |
|
|
732 | =item unsigned int ev_depth (loop) |
|
|
733 | |
|
|
734 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
736 | |
|
|
737 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
739 | in which case it is higher. |
|
|
740 | |
|
|
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
539 | |
745 | |
540 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
541 | |
747 | |
542 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
543 | use. |
749 | use. |
… | |
… | |
548 | received events and started processing them. This timestamp does not |
754 | received events and started processing them. This timestamp does not |
549 | change as long as callbacks are being processed, and this is also the base |
755 | change as long as callbacks are being processed, and this is also the base |
550 | time used for relative timers. You can treat it as the timestamp of the |
756 | time used for relative timers. You can treat it as the timestamp of the |
551 | event occurring (or more correctly, libev finding out about it). |
757 | event occurring (or more correctly, libev finding out about it). |
552 | |
758 | |
|
|
759 | =item ev_now_update (loop) |
|
|
760 | |
|
|
761 | Establishes the current time by querying the kernel, updating the time |
|
|
762 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
763 | is usually done automatically within C<ev_run ()>. |
|
|
764 | |
|
|
765 | This function is rarely useful, but when some event callback runs for a |
|
|
766 | very long time without entering the event loop, updating libev's idea of |
|
|
767 | the current time is a good idea. |
|
|
768 | |
|
|
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
770 | |
|
|
771 | =item ev_suspend (loop) |
|
|
772 | |
|
|
773 | =item ev_resume (loop) |
|
|
774 | |
|
|
775 | These two functions suspend and resume an event loop, for use when the |
|
|
776 | loop is not used for a while and timeouts should not be processed. |
|
|
777 | |
|
|
778 | A typical use case would be an interactive program such as a game: When |
|
|
779 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
780 | would be best to handle timeouts as if no time had actually passed while |
|
|
781 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
782 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
783 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
784 | |
|
|
785 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
786 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
787 | will be rescheduled (that is, they will lose any events that would have |
|
|
788 | occurred while suspended). |
|
|
789 | |
|
|
790 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
791 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
792 | without a previous call to C<ev_suspend>. |
|
|
793 | |
|
|
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
795 | event loop time (see C<ev_now_update>). |
|
|
796 | |
553 | =item ev_loop (loop, int flags) |
797 | =item ev_run (loop, int flags) |
554 | |
798 | |
555 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
556 | after you initialised all your watchers and you want to start handling |
800 | after you have initialised all your watchers and you want to start |
557 | events. |
801 | handling events. It will ask the operating system for any new events, call |
|
|
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
803 | is why event loops are called I<loops>. |
558 | |
804 | |
559 | If the flags argument is specified as C<0>, it will not return until |
805 | If the flags argument is specified as C<0>, it will keep handling events |
560 | either no event watchers are active anymore or C<ev_unloop> was called. |
806 | until either no event watchers are active anymore or C<ev_break> was |
|
|
807 | called. |
561 | |
808 | |
562 | Please note that an explicit C<ev_unloop> is usually better than |
809 | Please note that an explicit C<ev_break> is usually better than |
563 | relying on all watchers to be stopped when deciding when a program has |
810 | relying on all watchers to be stopped when deciding when a program has |
564 | finished (especially in interactive programs), but having a program that |
811 | finished (especially in interactive programs), but having a program |
565 | automatically loops as long as it has to and no longer by virtue of |
812 | that automatically loops as long as it has to and no longer by virtue |
566 | relying on its watchers stopping correctly is a thing of beauty. |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
814 | beauty. |
567 | |
815 | |
|
|
816 | This function is also I<mostly> exception-safe - you can break out of |
|
|
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
820 | |
568 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
569 | those events and any outstanding ones, but will not block your process in |
822 | those events and any already outstanding ones, but will not wait and |
570 | case there are no events and will return after one iteration of the loop. |
823 | block your process in case there are no events and will return after one |
|
|
824 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
825 | events while doing lengthy calculations, to keep the program responsive. |
571 | |
826 | |
572 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
827 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
573 | neccessary) and will handle those and any outstanding ones. It will block |
828 | necessary) and will handle those and any already outstanding ones. It |
574 | your process until at least one new event arrives, and will return after |
829 | will block your process until at least one new event arrives (which could |
575 | one iteration of the loop. This is useful if you are waiting for some |
830 | be an event internal to libev itself, so there is no guarantee that a |
576 | external event in conjunction with something not expressible using other |
831 | user-registered callback will be called), and will return after one |
|
|
832 | iteration of the loop. |
|
|
833 | |
|
|
834 | This is useful if you are waiting for some external event in conjunction |
|
|
835 | with something not expressible using other libev watchers (i.e. "roll your |
577 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
578 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
579 | |
838 | |
580 | Here are the gory details of what C<ev_loop> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
581 | |
842 | |
|
|
843 | - Increment loop depth. |
|
|
844 | - Reset the ev_break status. |
582 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
|
|
846 | LOOP: |
583 | * If EVFLAG_FORKCHECK was used, check for a fork. |
847 | - If EVFLAG_FORKCHECK was used, check for a fork. |
584 | - If a fork was detected, queue and call all fork watchers. |
848 | - If a fork was detected (by any means), queue and call all fork watchers. |
585 | - Queue and call all prepare watchers. |
849 | - Queue and call all prepare watchers. |
|
|
850 | - If ev_break was called, goto FINISH. |
586 | - If we have been forked, recreate the kernel state. |
851 | - If we have been forked, detach and recreate the kernel state |
|
|
852 | as to not disturb the other process. |
587 | - Update the kernel state with all outstanding changes. |
853 | - Update the kernel state with all outstanding changes. |
588 | - Update the "event loop time". |
854 | - Update the "event loop time" (ev_now ()). |
589 | - Calculate for how long to sleep or block, if at all |
855 | - Calculate for how long to sleep or block, if at all |
590 | (active idle watchers, EVLOOP_NONBLOCK or not having |
856 | (active idle watchers, EVRUN_NOWAIT or not having |
591 | any active watchers at all will result in not sleeping). |
857 | any active watchers at all will result in not sleeping). |
592 | - Sleep if the I/O and timer collect interval say so. |
858 | - Sleep if the I/O and timer collect interval say so. |
|
|
859 | - Increment loop iteration counter. |
593 | - Block the process, waiting for any events. |
860 | - Block the process, waiting for any events. |
594 | - Queue all outstanding I/O (fd) events. |
861 | - Queue all outstanding I/O (fd) events. |
595 | - Update the "event loop time" and do time jump handling. |
862 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
596 | - Queue all outstanding timers. |
863 | - Queue all expired timers. |
597 | - Queue all outstanding periodics. |
864 | - Queue all expired periodics. |
598 | - If no events are pending now, queue all idle watchers. |
865 | - Queue all idle watchers with priority higher than that of pending events. |
599 | - Queue all check watchers. |
866 | - Queue all check watchers. |
600 | - Call all queued watchers in reverse order (i.e. check watchers first). |
867 | - Call all queued watchers in reverse order (i.e. check watchers first). |
601 | Signals and child watchers are implemented as I/O watchers, and will |
868 | Signals and child watchers are implemented as I/O watchers, and will |
602 | be handled here by queueing them when their watcher gets executed. |
869 | be handled here by queueing them when their watcher gets executed. |
603 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
870 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
604 | were used, or there are no active watchers, return, otherwise |
871 | were used, or there are no active watchers, goto FINISH, otherwise |
605 | continue with step *. |
872 | continue with step LOOP. |
|
|
873 | FINISH: |
|
|
874 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
875 | - Decrement the loop depth. |
|
|
876 | - Return. |
606 | |
877 | |
607 | Example: Queue some jobs and then loop until no events are outstanding |
878 | Example: Queue some jobs and then loop until no events are outstanding |
608 | anymore. |
879 | anymore. |
609 | |
880 | |
610 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
611 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
612 | ev_loop (my_loop, 0); |
883 | ev_run (my_loop, 0); |
613 | ... jobs done. yeah! |
884 | ... jobs done or somebody called break. yeah! |
614 | |
885 | |
615 | =item ev_unloop (loop, how) |
886 | =item ev_break (loop, how) |
616 | |
887 | |
617 | Can be used to make a call to C<ev_loop> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
618 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
619 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
890 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
620 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
891 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
621 | |
892 | |
622 | This "unloop state" will be cleared when entering C<ev_loop> again. |
893 | This "break state" will be cleared on the next call to C<ev_run>. |
|
|
894 | |
|
|
895 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
896 | which case it will have no effect. |
623 | |
897 | |
624 | =item ev_ref (loop) |
898 | =item ev_ref (loop) |
625 | |
899 | |
626 | =item ev_unref (loop) |
900 | =item ev_unref (loop) |
627 | |
901 | |
628 | Ref/unref can be used to add or remove a reference count on the event |
902 | Ref/unref can be used to add or remove a reference count on the event |
629 | loop: Every watcher keeps one reference, and as long as the reference |
903 | loop: Every watcher keeps one reference, and as long as the reference |
630 | count is nonzero, C<ev_loop> will not return on its own. If you have |
904 | count is nonzero, C<ev_run> will not return on its own. |
631 | a watcher you never unregister that should not keep C<ev_loop> from |
905 | |
632 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
906 | This is useful when you have a watcher that you never intend to |
|
|
907 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
908 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
909 | before stopping it. |
|
|
910 | |
633 | example, libev itself uses this for its internal signal pipe: It is not |
911 | As an example, libev itself uses this for its internal signal pipe: It |
634 | visible to the libev user and should not keep C<ev_loop> from exiting if |
912 | is not visible to the libev user and should not keep C<ev_run> from |
635 | no event watchers registered by it are active. It is also an excellent |
913 | exiting if no event watchers registered by it are active. It is also an |
636 | way to do this for generic recurring timers or from within third-party |
914 | excellent way to do this for generic recurring timers or from within |
637 | libraries. Just remember to I<unref after start> and I<ref before stop> |
915 | third-party libraries. Just remember to I<unref after start> and I<ref |
638 | (but only if the watcher wasn't active before, or was active before, |
916 | before stop> (but only if the watcher wasn't active before, or was active |
639 | respectively). |
917 | before, respectively. Note also that libev might stop watchers itself |
|
|
918 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
919 | in the callback). |
640 | |
920 | |
641 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
921 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
642 | running when nothing else is active. |
922 | running when nothing else is active. |
643 | |
923 | |
644 | struct ev_signal exitsig; |
924 | ev_signal exitsig; |
645 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
925 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
646 | ev_signal_start (loop, &exitsig); |
926 | ev_signal_start (loop, &exitsig); |
647 | evf_unref (loop); |
927 | ev_unref (loop); |
648 | |
928 | |
649 | Example: For some weird reason, unregister the above signal handler again. |
929 | Example: For some weird reason, unregister the above signal handler again. |
650 | |
930 | |
651 | ev_ref (loop); |
931 | ev_ref (loop); |
652 | ev_signal_stop (loop, &exitsig); |
932 | ev_signal_stop (loop, &exitsig); |
653 | |
933 | |
654 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
934 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
655 | |
935 | |
656 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
936 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
657 | |
937 | |
658 | These advanced functions influence the time that libev will spend waiting |
938 | These advanced functions influence the time that libev will spend waiting |
659 | for events. Both are by default C<0>, meaning that libev will try to |
939 | for events. Both time intervals are by default C<0>, meaning that libev |
660 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
940 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
941 | latency. |
661 | |
942 | |
662 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
943 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
663 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
944 | allows libev to delay invocation of I/O and timer/periodic callbacks |
664 | increase efficiency of loop iterations. |
945 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
946 | opportunities). |
665 | |
947 | |
666 | The background is that sometimes your program runs just fast enough to |
948 | The idea is that sometimes your program runs just fast enough to handle |
667 | handle one (or very few) event(s) per loop iteration. While this makes |
949 | one (or very few) event(s) per loop iteration. While this makes the |
668 | the program responsive, it also wastes a lot of CPU time to poll for new |
950 | program responsive, it also wastes a lot of CPU time to poll for new |
669 | events, especially with backends like C<select ()> which have a high |
951 | events, especially with backends like C<select ()> which have a high |
670 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
671 | |
953 | |
672 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
673 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
674 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
675 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
676 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
959 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
677 | |
962 | |
678 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
679 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
680 | latency (the watcher callback will be called later). C<ev_io> watchers |
965 | latency/jitter/inexactness (the watcher callback will be called |
681 | will not be affected. Setting this to a non-null value will not introduce |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
682 | any overhead in libev. |
967 | value will not introduce any overhead in libev. |
683 | |
968 | |
684 | Many (busy) programs can usually benefit by setting the io collect |
969 | Many (busy) programs can usually benefit by setting the I/O collect |
685 | interval to a value near C<0.1> or so, which is often enough for |
970 | interval to a value near C<0.1> or so, which is often enough for |
686 | interactive servers (of course not for games), likewise for timeouts. It |
971 | interactive servers (of course not for games), likewise for timeouts. It |
687 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
972 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
688 | as this approsaches the timing granularity of most systems. |
973 | as this approaches the timing granularity of most systems. Note that if |
|
|
974 | you do transactions with the outside world and you can't increase the |
|
|
975 | parallelity, then this setting will limit your transaction rate (if you |
|
|
976 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
977 | then you can't do more than 100 transactions per second). |
|
|
978 | |
|
|
979 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
980 | saving power, as the program will "bundle" timer callback invocations that |
|
|
981 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
982 | times the process sleeps and wakes up again. Another useful technique to |
|
|
983 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
984 | they fire on, say, one-second boundaries only. |
|
|
985 | |
|
|
986 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
987 | more often than 100 times per second: |
|
|
988 | |
|
|
989 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
990 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
991 | |
|
|
992 | =item ev_invoke_pending (loop) |
|
|
993 | |
|
|
994 | This call will simply invoke all pending watchers while resetting their |
|
|
995 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
996 | but when overriding the invoke callback this call comes handy. This |
|
|
997 | function can be invoked from a watcher - this can be useful for example |
|
|
998 | when you want to do some lengthy calculation and want to pass further |
|
|
999 | event handling to another thread (you still have to make sure only one |
|
|
1000 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1001 | |
|
|
1002 | =item int ev_pending_count (loop) |
|
|
1003 | |
|
|
1004 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1005 | are pending. |
|
|
1006 | |
|
|
1007 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1008 | |
|
|
1009 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1010 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1011 | this callback instead. This is useful, for example, when you want to |
|
|
1012 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1013 | |
|
|
1014 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1015 | callback. |
|
|
1016 | |
|
|
1017 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
1018 | |
|
|
1019 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1021 | each call to a libev function. |
|
|
1022 | |
|
|
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1024 | to wait for it to return. One way around this is to wake up the event |
|
|
1025 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
|
|
1026 | I<release> and I<acquire> callbacks on the loop. |
|
|
1027 | |
|
|
1028 | When set, then C<release> will be called just before the thread is |
|
|
1029 | suspended waiting for new events, and C<acquire> is called just |
|
|
1030 | afterwards. |
|
|
1031 | |
|
|
1032 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1033 | C<acquire> will just call the mutex_lock function again. |
|
|
1034 | |
|
|
1035 | While event loop modifications are allowed between invocations of |
|
|
1036 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1037 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1038 | have no effect on the set of file descriptors being watched, or the time |
|
|
1039 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1040 | to take note of any changes you made. |
|
|
1041 | |
|
|
1042 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1043 | invocations of C<release> and C<acquire>. |
|
|
1044 | |
|
|
1045 | See also the locking example in the C<THREADS> section later in this |
|
|
1046 | document. |
|
|
1047 | |
|
|
1048 | =item ev_set_userdata (loop, void *data) |
|
|
1049 | |
|
|
1050 | =item void *ev_userdata (loop) |
|
|
1051 | |
|
|
1052 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1053 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1054 | C<0>. |
|
|
1055 | |
|
|
1056 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1057 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1058 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1059 | any other purpose as well. |
|
|
1060 | |
|
|
1061 | =item ev_verify (loop) |
|
|
1062 | |
|
|
1063 | This function only does something when C<EV_VERIFY> support has been |
|
|
1064 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
1065 | through all internal structures and checks them for validity. If anything |
|
|
1066 | is found to be inconsistent, it will print an error message to standard |
|
|
1067 | error and call C<abort ()>. |
|
|
1068 | |
|
|
1069 | This can be used to catch bugs inside libev itself: under normal |
|
|
1070 | circumstances, this function will never abort as of course libev keeps its |
|
|
1071 | data structures consistent. |
689 | |
1072 | |
690 | =back |
1073 | =back |
691 | |
1074 | |
692 | |
1075 | |
693 | =head1 ANATOMY OF A WATCHER |
1076 | =head1 ANATOMY OF A WATCHER |
694 | |
1077 | |
|
|
1078 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1079 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1080 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1081 | |
695 | A watcher is a structure that you create and register to record your |
1082 | A watcher is an opaque structure that you allocate and register to record |
696 | interest in some event. For instance, if you want to wait for STDIN to |
1083 | your interest in some event. To make a concrete example, imagine you want |
697 | become readable, you would create an C<ev_io> watcher for that: |
1084 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1085 | for that: |
698 | |
1086 | |
699 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1087 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
700 | { |
1088 | { |
701 | ev_io_stop (w); |
1089 | ev_io_stop (w); |
702 | ev_unloop (loop, EVUNLOOP_ALL); |
1090 | ev_break (loop, EVBREAK_ALL); |
703 | } |
1091 | } |
704 | |
1092 | |
705 | struct ev_loop *loop = ev_default_loop (0); |
1093 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1094 | |
706 | struct ev_io stdin_watcher; |
1095 | ev_io stdin_watcher; |
|
|
1096 | |
707 | ev_init (&stdin_watcher, my_cb); |
1097 | ev_init (&stdin_watcher, my_cb); |
708 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1098 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
709 | ev_io_start (loop, &stdin_watcher); |
1099 | ev_io_start (loop, &stdin_watcher); |
|
|
1100 | |
710 | ev_loop (loop, 0); |
1101 | ev_run (loop, 0); |
711 | |
1102 | |
712 | As you can see, you are responsible for allocating the memory for your |
1103 | As you can see, you are responsible for allocating the memory for your |
713 | watcher structures (and it is usually a bad idea to do this on the stack, |
1104 | watcher structures (and it is I<usually> a bad idea to do this on the |
714 | although this can sometimes be quite valid). |
1105 | stack). |
715 | |
1106 | |
|
|
1107 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1108 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1109 | |
716 | Each watcher structure must be initialised by a call to C<ev_init |
1110 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
717 | (watcher *, callback)>, which expects a callback to be provided. This |
1111 | *, callback)>, which expects a callback to be provided. This callback is |
718 | callback gets invoked each time the event occurs (or, in the case of io |
1112 | invoked each time the event occurs (or, in the case of I/O watchers, each |
719 | watchers, each time the event loop detects that the file descriptor given |
1113 | time the event loop detects that the file descriptor given is readable |
720 | is readable and/or writable). |
1114 | and/or writable). |
721 | |
1115 | |
722 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1116 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
723 | with arguments specific to this watcher type. There is also a macro |
1117 | macro to configure it, with arguments specific to the watcher type. There |
724 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1118 | is also a macro to combine initialisation and setting in one call: C<< |
725 | (watcher *, callback, ...) >>. |
1119 | ev_TYPE_init (watcher *, callback, ...) >>. |
726 | |
1120 | |
727 | To make the watcher actually watch out for events, you have to start it |
1121 | To make the watcher actually watch out for events, you have to start it |
728 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1122 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
729 | *) >>), and you can stop watching for events at any time by calling the |
1123 | *) >>), and you can stop watching for events at any time by calling the |
730 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1124 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
731 | |
1125 | |
732 | As long as your watcher is active (has been started but not stopped) you |
1126 | As long as your watcher is active (has been started but not stopped) you |
733 | must not touch the values stored in it. Most specifically you must never |
1127 | must not touch the values stored in it. Most specifically you must never |
734 | reinitialise it or call its C<set> macro. |
1128 | reinitialise it or call its C<ev_TYPE_set> macro. |
735 | |
1129 | |
736 | Each and every callback receives the event loop pointer as first, the |
1130 | Each and every callback receives the event loop pointer as first, the |
737 | registered watcher structure as second, and a bitset of received events as |
1131 | registered watcher structure as second, and a bitset of received events as |
738 | third argument. |
1132 | third argument. |
739 | |
1133 | |
… | |
… | |
748 | =item C<EV_WRITE> |
1142 | =item C<EV_WRITE> |
749 | |
1143 | |
750 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1144 | The file descriptor in the C<ev_io> watcher has become readable and/or |
751 | writable. |
1145 | writable. |
752 | |
1146 | |
753 | =item C<EV_TIMEOUT> |
1147 | =item C<EV_TIMER> |
754 | |
1148 | |
755 | The C<ev_timer> watcher has timed out. |
1149 | The C<ev_timer> watcher has timed out. |
756 | |
1150 | |
757 | =item C<EV_PERIODIC> |
1151 | =item C<EV_PERIODIC> |
758 | |
1152 | |
… | |
… | |
776 | |
1170 | |
777 | =item C<EV_PREPARE> |
1171 | =item C<EV_PREPARE> |
778 | |
1172 | |
779 | =item C<EV_CHECK> |
1173 | =item C<EV_CHECK> |
780 | |
1174 | |
781 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1175 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
782 | to gather new events, and all C<ev_check> watchers are invoked just after |
1176 | to gather new events, and all C<ev_check> watchers are invoked just after |
783 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1177 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
784 | received events. Callbacks of both watcher types can start and stop as |
1178 | received events. Callbacks of both watcher types can start and stop as |
785 | many watchers as they want, and all of them will be taken into account |
1179 | many watchers as they want, and all of them will be taken into account |
786 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1180 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
787 | C<ev_loop> from blocking). |
1181 | C<ev_run> from blocking). |
788 | |
1182 | |
789 | =item C<EV_EMBED> |
1183 | =item C<EV_EMBED> |
790 | |
1184 | |
791 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1185 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
792 | |
1186 | |
793 | =item C<EV_FORK> |
1187 | =item C<EV_FORK> |
794 | |
1188 | |
795 | The event loop has been resumed in the child process after fork (see |
1189 | The event loop has been resumed in the child process after fork (see |
796 | C<ev_fork>). |
1190 | C<ev_fork>). |
797 | |
1191 | |
|
|
1192 | =item C<EV_CLEANUP> |
|
|
1193 | |
|
|
1194 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1195 | |
798 | =item C<EV_ASYNC> |
1196 | =item C<EV_ASYNC> |
799 | |
1197 | |
800 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1198 | The given async watcher has been asynchronously notified (see C<ev_async>). |
801 | |
1199 | |
|
|
1200 | =item C<EV_CUSTOM> |
|
|
1201 | |
|
|
1202 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1203 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1204 | |
802 | =item C<EV_ERROR> |
1205 | =item C<EV_ERROR> |
803 | |
1206 | |
804 | An unspecified error has occured, the watcher has been stopped. This might |
1207 | An unspecified error has occurred, the watcher has been stopped. This might |
805 | happen because the watcher could not be properly started because libev |
1208 | happen because the watcher could not be properly started because libev |
806 | ran out of memory, a file descriptor was found to be closed or any other |
1209 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1210 | problem. Libev considers these application bugs. |
|
|
1211 | |
807 | problem. You best act on it by reporting the problem and somehow coping |
1212 | You best act on it by reporting the problem and somehow coping with the |
808 | with the watcher being stopped. |
1213 | watcher being stopped. Note that well-written programs should not receive |
|
|
1214 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1215 | bug in your program. |
809 | |
1216 | |
810 | Libev will usually signal a few "dummy" events together with an error, |
1217 | Libev will usually signal a few "dummy" events together with an error, for |
811 | for example it might indicate that a fd is readable or writable, and if |
1218 | example it might indicate that a fd is readable or writable, and if your |
812 | your callbacks is well-written it can just attempt the operation and cope |
1219 | callbacks is well-written it can just attempt the operation and cope with |
813 | with the error from read() or write(). This will not work in multithreaded |
1220 | the error from read() or write(). This will not work in multi-threaded |
814 | programs, though, so beware. |
1221 | programs, though, as the fd could already be closed and reused for another |
|
|
1222 | thing, so beware. |
815 | |
1223 | |
816 | =back |
1224 | =back |
817 | |
1225 | |
818 | =head2 GENERIC WATCHER FUNCTIONS |
1226 | =head2 GENERIC WATCHER FUNCTIONS |
819 | |
|
|
820 | In the following description, C<TYPE> stands for the watcher type, |
|
|
821 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
822 | |
1227 | |
823 | =over 4 |
1228 | =over 4 |
824 | |
1229 | |
825 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1230 | =item C<ev_init> (ev_TYPE *watcher, callback) |
826 | |
1231 | |
… | |
… | |
832 | which rolls both calls into one. |
1237 | which rolls both calls into one. |
833 | |
1238 | |
834 | You can reinitialise a watcher at any time as long as it has been stopped |
1239 | You can reinitialise a watcher at any time as long as it has been stopped |
835 | (or never started) and there are no pending events outstanding. |
1240 | (or never started) and there are no pending events outstanding. |
836 | |
1241 | |
837 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1242 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
838 | int revents)>. |
1243 | int revents)>. |
839 | |
1244 | |
|
|
1245 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1246 | |
|
|
1247 | ev_io w; |
|
|
1248 | ev_init (&w, my_cb); |
|
|
1249 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1250 | |
840 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1251 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
841 | |
1252 | |
842 | This macro initialises the type-specific parts of a watcher. You need to |
1253 | This macro initialises the type-specific parts of a watcher. You need to |
843 | call C<ev_init> at least once before you call this macro, but you can |
1254 | call C<ev_init> at least once before you call this macro, but you can |
844 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1255 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
845 | macro on a watcher that is active (it can be pending, however, which is a |
1256 | macro on a watcher that is active (it can be pending, however, which is a |
846 | difference to the C<ev_init> macro). |
1257 | difference to the C<ev_init> macro). |
847 | |
1258 | |
848 | Although some watcher types do not have type-specific arguments |
1259 | Although some watcher types do not have type-specific arguments |
849 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1260 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
850 | |
1261 | |
|
|
1262 | See C<ev_init>, above, for an example. |
|
|
1263 | |
851 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1264 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
852 | |
1265 | |
853 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1266 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
854 | calls into a single call. This is the most convinient method to initialise |
1267 | calls into a single call. This is the most convenient method to initialise |
855 | a watcher. The same limitations apply, of course. |
1268 | a watcher. The same limitations apply, of course. |
856 | |
1269 | |
|
|
1270 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1271 | |
|
|
1272 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1273 | |
857 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1274 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
858 | |
1275 | |
859 | Starts (activates) the given watcher. Only active watchers will receive |
1276 | Starts (activates) the given watcher. Only active watchers will receive |
860 | events. If the watcher is already active nothing will happen. |
1277 | events. If the watcher is already active nothing will happen. |
861 | |
1278 | |
|
|
1279 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1280 | whole section. |
|
|
1281 | |
|
|
1282 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1283 | |
862 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1284 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
863 | |
1285 | |
864 | Stops the given watcher again (if active) and clears the pending |
1286 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1287 | the watcher was active or not). |
|
|
1288 | |
865 | status. It is possible that stopped watchers are pending (for example, |
1289 | It is possible that stopped watchers are pending - for example, |
866 | non-repeating timers are being stopped when they become pending), but |
1290 | non-repeating timers are being stopped when they become pending - but |
867 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1291 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
868 | you want to free or reuse the memory used by the watcher it is therefore a |
1292 | pending. If you want to free or reuse the memory used by the watcher it is |
869 | good idea to always call its C<ev_TYPE_stop> function. |
1293 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
870 | |
1294 | |
871 | =item bool ev_is_active (ev_TYPE *watcher) |
1295 | =item bool ev_is_active (ev_TYPE *watcher) |
872 | |
1296 | |
873 | Returns a true value iff the watcher is active (i.e. it has been started |
1297 | Returns a true value iff the watcher is active (i.e. it has been started |
874 | and not yet been stopped). As long as a watcher is active you must not modify |
1298 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
890 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1314 | =item ev_cb_set (ev_TYPE *watcher, callback) |
891 | |
1315 | |
892 | Change the callback. You can change the callback at virtually any time |
1316 | Change the callback. You can change the callback at virtually any time |
893 | (modulo threads). |
1317 | (modulo threads). |
894 | |
1318 | |
895 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1319 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
896 | |
1320 | |
897 | =item int ev_priority (ev_TYPE *watcher) |
1321 | =item int ev_priority (ev_TYPE *watcher) |
898 | |
1322 | |
899 | Set and query the priority of the watcher. The priority is a small |
1323 | Set and query the priority of the watcher. The priority is a small |
900 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1324 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
901 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1325 | (default: C<-2>). Pending watchers with higher priority will be invoked |
902 | before watchers with lower priority, but priority will not keep watchers |
1326 | before watchers with lower priority, but priority will not keep watchers |
903 | from being executed (except for C<ev_idle> watchers). |
1327 | from being executed (except for C<ev_idle> watchers). |
904 | |
1328 | |
905 | This means that priorities are I<only> used for ordering callback |
|
|
906 | invocation after new events have been received. This is useful, for |
|
|
907 | example, to reduce latency after idling, or more often, to bind two |
|
|
908 | watchers on the same event and make sure one is called first. |
|
|
909 | |
|
|
910 | If you need to suppress invocation when higher priority events are pending |
1329 | If you need to suppress invocation when higher priority events are pending |
911 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1330 | you need to look at C<ev_idle> watchers, which provide this functionality. |
912 | |
1331 | |
913 | You I<must not> change the priority of a watcher as long as it is active or |
1332 | You I<must not> change the priority of a watcher as long as it is active or |
914 | pending. |
1333 | pending. |
915 | |
1334 | |
|
|
1335 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1336 | fine, as long as you do not mind that the priority value you query might |
|
|
1337 | or might not have been clamped to the valid range. |
|
|
1338 | |
916 | The default priority used by watchers when no priority has been set is |
1339 | The default priority used by watchers when no priority has been set is |
917 | always C<0>, which is supposed to not be too high and not be too low :). |
1340 | always C<0>, which is supposed to not be too high and not be too low :). |
918 | |
1341 | |
919 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1342 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
920 | fine, as long as you do not mind that the priority value you query might |
1343 | priorities. |
921 | or might not have been adjusted to be within valid range. |
|
|
922 | |
1344 | |
923 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1345 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
924 | |
1346 | |
925 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1347 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
926 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1348 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
927 | can deal with that fact. |
1349 | can deal with that fact, as both are simply passed through to the |
|
|
1350 | callback. |
928 | |
1351 | |
929 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1352 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
930 | |
1353 | |
931 | If the watcher is pending, this function returns clears its pending status |
1354 | If the watcher is pending, this function clears its pending status and |
932 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1355 | returns its C<revents> bitset (as if its callback was invoked). If the |
933 | watcher isn't pending it does nothing and returns C<0>. |
1356 | watcher isn't pending it does nothing and returns C<0>. |
934 | |
1357 | |
|
|
1358 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1359 | callback to be invoked, which can be accomplished with this function. |
|
|
1360 | |
|
|
1361 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1362 | |
|
|
1363 | Feeds the given event set into the event loop, as if the specified event |
|
|
1364 | had happened for the specified watcher (which must be a pointer to an |
|
|
1365 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1366 | not free the watcher as long as it has pending events. |
|
|
1367 | |
|
|
1368 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1369 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1370 | not started in the first place. |
|
|
1371 | |
|
|
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1373 | functions that do not need a watcher. |
|
|
1374 | |
935 | =back |
1375 | =back |
936 | |
1376 | |
|
|
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1378 | OWN COMPOSITE WATCHERS> idioms. |
937 | |
1379 | |
938 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1380 | =head2 WATCHER STATES |
939 | |
1381 | |
940 | Each watcher has, by default, a member C<void *data> that you can change |
1382 | There are various watcher states mentioned throughout this manual - |
941 | and read at any time, libev will completely ignore it. This can be used |
1383 | active, pending and so on. In this section these states and the rules to |
942 | to associate arbitrary data with your watcher. If you need more data and |
1384 | transition between them will be described in more detail - and while these |
943 | don't want to allocate memory and store a pointer to it in that data |
1385 | rules might look complicated, they usually do "the right thing". |
944 | member, you can also "subclass" the watcher type and provide your own |
|
|
945 | data: |
|
|
946 | |
1386 | |
947 | struct my_io |
1387 | =over 4 |
948 | { |
|
|
949 | struct ev_io io; |
|
|
950 | int otherfd; |
|
|
951 | void *somedata; |
|
|
952 | struct whatever *mostinteresting; |
|
|
953 | } |
|
|
954 | |
1388 | |
955 | And since your callback will be called with a pointer to the watcher, you |
1389 | =item initialiased |
956 | can cast it back to your own type: |
|
|
957 | |
1390 | |
958 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1391 | Before a watcher can be registered with the event loop it has to be |
959 | { |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
960 | struct my_io *w = (struct my_io *)w_; |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
961 | ... |
|
|
962 | } |
|
|
963 | |
1394 | |
964 | More interesting and less C-conformant ways of casting your callback type |
1395 | In this state it is simply some block of memory that is suitable for |
965 | instead have been omitted. |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1397 | will - as long as you either keep the memory contents intact, or call |
|
|
1398 | C<ev_TYPE_init> again. |
966 | |
1399 | |
967 | Another common scenario is having some data structure with multiple |
1400 | =item started/running/active |
968 | watchers: |
|
|
969 | |
1401 | |
970 | struct my_biggy |
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
971 | { |
1403 | property of the event loop, and is actively waiting for events. While in |
972 | int some_data; |
1404 | this state it cannot be accessed (except in a few documented ways), moved, |
973 | ev_timer t1; |
1405 | freed or anything else - the only legal thing is to keep a pointer to it, |
974 | ev_timer t2; |
1406 | and call libev functions on it that are documented to work on active watchers. |
975 | } |
|
|
976 | |
1407 | |
977 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1408 | =item pending |
978 | you need to use C<offsetof>: |
|
|
979 | |
1409 | |
980 | #include <stddef.h> |
1410 | If a watcher is active and libev determines that an event it is interested |
|
|
1411 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1412 | stay in this pending state until either it is stopped or its callback is |
|
|
1413 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1414 | callback. |
981 | |
1415 | |
|
|
1416 | The watcher might or might not be active while it is pending (for example, |
|
|
1417 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1418 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1419 | but it is still property of the event loop at this time, so cannot be |
|
|
1420 | moved, freed or reused. And if it is active the rules described in the |
|
|
1421 | previous item still apply. |
|
|
1422 | |
|
|
1423 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1424 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1425 | active. |
|
|
1426 | |
|
|
1427 | =item stopped |
|
|
1428 | |
|
|
1429 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1430 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1431 | latter will clear any pending state the watcher might be in, regardless |
|
|
1432 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1433 | freeing it is often a good idea. |
|
|
1434 | |
|
|
1435 | While stopped (and not pending) the watcher is essentially in the |
|
|
1436 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
|
|
1439 | |
|
|
1440 | =back |
|
|
1441 | |
|
|
1442 | =head2 WATCHER PRIORITY MODELS |
|
|
1443 | |
|
|
1444 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1445 | integers that influence the ordering of event callback invocation |
|
|
1446 | between watchers in some way, all else being equal. |
|
|
1447 | |
|
|
1448 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1449 | description for the more technical details such as the actual priority |
|
|
1450 | range. |
|
|
1451 | |
|
|
1452 | There are two common ways how these these priorities are being interpreted |
|
|
1453 | by event loops: |
|
|
1454 | |
|
|
1455 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1456 | of lower priority watchers, which means as long as higher priority |
|
|
1457 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1458 | |
|
|
1459 | The less common only-for-ordering model uses priorities solely to order |
|
|
1460 | callback invocation within a single event loop iteration: Higher priority |
|
|
1461 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1462 | before polling for new events. |
|
|
1463 | |
|
|
1464 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1465 | except for idle watchers (which use the lock-out model). |
|
|
1466 | |
|
|
1467 | The rationale behind this is that implementing the lock-out model for |
|
|
1468 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1469 | libraries will just poll for the same events again and again as long as |
|
|
1470 | their callbacks have not been executed, which is very inefficient in the |
|
|
1471 | common case of one high-priority watcher locking out a mass of lower |
|
|
1472 | priority ones. |
|
|
1473 | |
|
|
1474 | Static (ordering) priorities are most useful when you have two or more |
|
|
1475 | watchers handling the same resource: a typical usage example is having an |
|
|
1476 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1477 | timeouts. Under load, data might be received while the program handles |
|
|
1478 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1479 | handler will be executed before checking for data. In that case, giving |
|
|
1480 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1481 | handled first even under adverse conditions (which is usually, but not |
|
|
1482 | always, what you want). |
|
|
1483 | |
|
|
1484 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1485 | will only be executed when no same or higher priority watchers have |
|
|
1486 | received events, they can be used to implement the "lock-out" model when |
|
|
1487 | required. |
|
|
1488 | |
|
|
1489 | For example, to emulate how many other event libraries handle priorities, |
|
|
1490 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1491 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1492 | processing is done in the idle watcher callback. This causes libev to |
|
|
1493 | continuously poll and process kernel event data for the watcher, but when |
|
|
1494 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1495 | workable. |
|
|
1496 | |
|
|
1497 | Usually, however, the lock-out model implemented that way will perform |
|
|
1498 | miserably under the type of load it was designed to handle. In that case, |
|
|
1499 | it might be preferable to stop the real watcher before starting the |
|
|
1500 | idle watcher, so the kernel will not have to process the event in case |
|
|
1501 | the actual processing will be delayed for considerable time. |
|
|
1502 | |
|
|
1503 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1504 | priority than the default, and which should only process data when no |
|
|
1505 | other events are pending: |
|
|
1506 | |
|
|
1507 | ev_idle idle; // actual processing watcher |
|
|
1508 | ev_io io; // actual event watcher |
|
|
1509 | |
982 | static void |
1510 | static void |
983 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1511 | io_cb (EV_P_ ev_io *w, int revents) |
984 | { |
1512 | { |
985 | struct my_biggy big = (struct my_biggy * |
1513 | // stop the I/O watcher, we received the event, but |
986 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1514 | // are not yet ready to handle it. |
|
|
1515 | ev_io_stop (EV_A_ w); |
|
|
1516 | |
|
|
1517 | // start the idle watcher to handle the actual event. |
|
|
1518 | // it will not be executed as long as other watchers |
|
|
1519 | // with the default priority are receiving events. |
|
|
1520 | ev_idle_start (EV_A_ &idle); |
987 | } |
1521 | } |
988 | |
1522 | |
989 | static void |
1523 | static void |
990 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1524 | idle_cb (EV_P_ ev_idle *w, int revents) |
991 | { |
1525 | { |
992 | struct my_biggy big = (struct my_biggy * |
1526 | // actual processing |
993 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1527 | read (STDIN_FILENO, ...); |
|
|
1528 | |
|
|
1529 | // have to start the I/O watcher again, as |
|
|
1530 | // we have handled the event |
|
|
1531 | ev_io_start (EV_P_ &io); |
994 | } |
1532 | } |
|
|
1533 | |
|
|
1534 | // initialisation |
|
|
1535 | ev_idle_init (&idle, idle_cb); |
|
|
1536 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1537 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1538 | |
|
|
1539 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1540 | low-priority connections can not be locked out forever under load. This |
|
|
1541 | enables your program to keep a lower latency for important connections |
|
|
1542 | during short periods of high load, while not completely locking out less |
|
|
1543 | important ones. |
995 | |
1544 | |
996 | |
1545 | |
997 | =head1 WATCHER TYPES |
1546 | =head1 WATCHER TYPES |
998 | |
1547 | |
999 | This section describes each watcher in detail, but will not repeat |
1548 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1023 | In general you can register as many read and/or write event watchers per |
1572 | In general you can register as many read and/or write event watchers per |
1024 | fd as you want (as long as you don't confuse yourself). Setting all file |
1573 | fd as you want (as long as you don't confuse yourself). Setting all file |
1025 | descriptors to non-blocking mode is also usually a good idea (but not |
1574 | descriptors to non-blocking mode is also usually a good idea (but not |
1026 | required if you know what you are doing). |
1575 | required if you know what you are doing). |
1027 | |
1576 | |
1028 | If you must do this, then force the use of a known-to-be-good backend |
|
|
1029 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
|
|
1030 | C<EVBACKEND_POLL>). |
|
|
1031 | |
|
|
1032 | Another thing you have to watch out for is that it is quite easy to |
1577 | Another thing you have to watch out for is that it is quite easy to |
1033 | receive "spurious" readyness notifications, that is your callback might |
1578 | receive "spurious" readiness notifications, that is, your callback might |
1034 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1035 | because there is no data. Not only are some backends known to create a |
1580 | because there is no data. It is very easy to get into this situation even |
1036 | lot of those (for example solaris ports), it is very easy to get into |
1581 | with a relatively standard program structure. Thus it is best to always |
1037 | this situation even with a relatively standard program structure. Thus |
1582 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1038 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1039 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1583 | preferable to a program hanging until some data arrives. |
1040 | |
1584 | |
1041 | If you cannot run the fd in non-blocking mode (for example you should not |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1042 | play around with an Xlib connection), then you have to seperately re-test |
1586 | not play around with an Xlib connection), then you have to separately |
1043 | whether a file descriptor is really ready with a known-to-be good interface |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1044 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1588 | interface such as poll (fortunately in the case of Xlib, it already does |
1045 | its own, so its quite safe to use). |
1589 | this on its own, so its quite safe to use). Some people additionally |
|
|
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1591 | indefinitely. |
|
|
1592 | |
|
|
1593 | But really, best use non-blocking mode. |
1046 | |
1594 | |
1047 | =head3 The special problem of disappearing file descriptors |
1595 | =head3 The special problem of disappearing file descriptors |
1048 | |
1596 | |
1049 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1597 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1050 | descriptor (either by calling C<close> explicitly or by any other means, |
1598 | descriptor (either due to calling C<close> explicitly or any other means, |
1051 | such as C<dup>). The reason is that you register interest in some file |
1599 | such as C<dup2>). The reason is that you register interest in some file |
1052 | descriptor, but when it goes away, the operating system will silently drop |
1600 | descriptor, but when it goes away, the operating system will silently drop |
1053 | this interest. If another file descriptor with the same number then is |
1601 | this interest. If another file descriptor with the same number then is |
1054 | registered with libev, there is no efficient way to see that this is, in |
1602 | registered with libev, there is no efficient way to see that this is, in |
1055 | fact, a different file descriptor. |
1603 | fact, a different file descriptor. |
1056 | |
1604 | |
… | |
… | |
1074 | |
1622 | |
1075 | There is no workaround possible except not registering events |
1623 | There is no workaround possible except not registering events |
1076 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1077 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1078 | |
1626 | |
|
|
1627 | =head3 The special problem of files |
|
|
1628 | |
|
|
1629 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1630 | representing files, and expect it to become ready when their program |
|
|
1631 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1632 | |
|
|
1633 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1634 | notification as soon as the kernel knows whether and how much data is |
|
|
1635 | there, and in the case of open files, that's always the case, so you |
|
|
1636 | always get a readiness notification instantly, and your read (or possibly |
|
|
1637 | write) will still block on the disk I/O. |
|
|
1638 | |
|
|
1639 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1640 | devices and so on, there is another party (the sender) that delivers data |
|
|
1641 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1642 | will not send data on its own, simply because it doesn't know what you |
|
|
1643 | wish to read - you would first have to request some data. |
|
|
1644 | |
|
|
1645 | Since files are typically not-so-well supported by advanced notification |
|
|
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1647 | to files, even though you should not use it. The reason for this is |
|
|
1648 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1649 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1650 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1651 | F</dev/urandom>), and even though the file might better be served with |
|
|
1652 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1653 | it "just works" instead of freezing. |
|
|
1654 | |
|
|
1655 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1656 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1657 | when you rarely read from a file instead of from a socket, and want to |
|
|
1658 | reuse the same code path. |
|
|
1659 | |
1079 | =head3 The special problem of fork |
1660 | =head3 The special problem of fork |
1080 | |
1661 | |
1081 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1662 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1082 | useless behaviour. Libev fully supports fork, but needs to be told about |
1663 | useless behaviour. Libev fully supports fork, but needs to be told about |
1083 | it in the child. |
1664 | it in the child if you want to continue to use it in the child. |
1084 | |
1665 | |
1085 | To support fork in your programs, you either have to call |
1666 | To support fork in your child processes, you have to call C<ev_loop_fork |
1086 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1667 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1087 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1088 | C<EVBACKEND_POLL>. |
|
|
1089 | |
1669 | |
|
|
1670 | =head3 The special problem of SIGPIPE |
|
|
1671 | |
|
|
1672 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
|
|
1673 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1674 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1675 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1676 | |
|
|
1677 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1678 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1679 | somewhere, as that would have given you a big clue). |
|
|
1680 | |
|
|
1681 | =head3 The special problem of accept()ing when you can't |
|
|
1682 | |
|
|
1683 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1684 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1685 | connection from the pending queue in all error cases. |
|
|
1686 | |
|
|
1687 | For example, larger servers often run out of file descriptors (because |
|
|
1688 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1689 | rejecting the connection, leading to libev signalling readiness on |
|
|
1690 | the next iteration again (the connection still exists after all), and |
|
|
1691 | typically causing the program to loop at 100% CPU usage. |
|
|
1692 | |
|
|
1693 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1694 | operating systems, there is usually little the app can do to remedy the |
|
|
1695 | situation, and no known thread-safe method of removing the connection to |
|
|
1696 | cope with overload is known (to me). |
|
|
1697 | |
|
|
1698 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1699 | - when the program encounters an overload, it will just loop until the |
|
|
1700 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1701 | event-based way to handle this situation, so it's the best one can do. |
|
|
1702 | |
|
|
1703 | A better way to handle the situation is to log any errors other than |
|
|
1704 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1705 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1706 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1707 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1708 | usage. |
|
|
1709 | |
|
|
1710 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1711 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1712 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1713 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1714 | clients under typical overload conditions. |
|
|
1715 | |
|
|
1716 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1717 | is often done with C<malloc> failures, but this results in an easy |
|
|
1718 | opportunity for a DoS attack. |
1090 | |
1719 | |
1091 | =head3 Watcher-Specific Functions |
1720 | =head3 Watcher-Specific Functions |
1092 | |
1721 | |
1093 | =over 4 |
1722 | =over 4 |
1094 | |
1723 | |
1095 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1724 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1096 | |
1725 | |
1097 | =item ev_io_set (ev_io *, int fd, int events) |
1726 | =item ev_io_set (ev_io *, int fd, int events) |
1098 | |
1727 | |
1099 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1728 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1100 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1729 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1101 | C<EV_READ | EV_WRITE> to receive the given events. |
1730 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1102 | |
1731 | |
1103 | =item int fd [read-only] |
1732 | =item int fd [read-only] |
1104 | |
1733 | |
1105 | The file descriptor being watched. |
1734 | The file descriptor being watched. |
1106 | |
1735 | |
… | |
… | |
1114 | |
1743 | |
1115 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1744 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1116 | readable, but only once. Since it is likely line-buffered, you could |
1745 | readable, but only once. Since it is likely line-buffered, you could |
1117 | attempt to read a whole line in the callback. |
1746 | attempt to read a whole line in the callback. |
1118 | |
1747 | |
1119 | static void |
1748 | static void |
1120 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1749 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1121 | { |
1750 | { |
1122 | ev_io_stop (loop, w); |
1751 | ev_io_stop (loop, w); |
1123 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1752 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1124 | } |
1753 | } |
1125 | |
1754 | |
1126 | ... |
1755 | ... |
1127 | struct ev_loop *loop = ev_default_init (0); |
1756 | struct ev_loop *loop = ev_default_init (0); |
1128 | struct ev_io stdin_readable; |
1757 | ev_io stdin_readable; |
1129 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1758 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1130 | ev_io_start (loop, &stdin_readable); |
1759 | ev_io_start (loop, &stdin_readable); |
1131 | ev_loop (loop, 0); |
1760 | ev_run (loop, 0); |
1132 | |
1761 | |
1133 | |
1762 | |
1134 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1763 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1135 | |
1764 | |
1136 | Timer watchers are simple relative timers that generate an event after a |
1765 | Timer watchers are simple relative timers that generate an event after a |
1137 | given time, and optionally repeating in regular intervals after that. |
1766 | given time, and optionally repeating in regular intervals after that. |
1138 | |
1767 | |
1139 | The timers are based on real time, that is, if you register an event that |
1768 | The timers are based on real time, that is, if you register an event that |
1140 | times out after an hour and you reset your system clock to last years |
1769 | times out after an hour and you reset your system clock to January last |
1141 | time, it will still time out after (roughly) and hour. "Roughly" because |
1770 | year, it will still time out after (roughly) one hour. "Roughly" because |
1142 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1143 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
|
|
1773 | |
|
|
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
|
|
1778 | iteration then the ones with earlier time-out values are invoked before |
|
|
1779 | ones of the same priority with later time-out values (but this is no |
|
|
1780 | longer true when a callback calls C<ev_run> recursively). |
|
|
1781 | |
|
|
1782 | =head3 Be smart about timeouts |
|
|
1783 | |
|
|
1784 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1786 | you want to raise some error after a while. |
|
|
1787 | |
|
|
1788 | What follows are some ways to handle this problem, from obvious and |
|
|
1789 | inefficient to smart and efficient. |
|
|
1790 | |
|
|
1791 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1792 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1793 | data or other life sign was received). |
|
|
1794 | |
|
|
1795 | =over 4 |
|
|
1796 | |
|
|
1797 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1798 | |
|
|
1799 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1800 | start the watcher: |
|
|
1801 | |
|
|
1802 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1803 | ev_timer_start (loop, timer); |
|
|
1804 | |
|
|
1805 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1806 | and start it again: |
|
|
1807 | |
|
|
1808 | ev_timer_stop (loop, timer); |
|
|
1809 | ev_timer_set (timer, 60., 0.); |
|
|
1810 | ev_timer_start (loop, timer); |
|
|
1811 | |
|
|
1812 | This is relatively simple to implement, but means that each time there is |
|
|
1813 | some activity, libev will first have to remove the timer from its internal |
|
|
1814 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1815 | still not a constant-time operation. |
|
|
1816 | |
|
|
1817 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1818 | |
|
|
1819 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1820 | C<ev_timer_start>. |
|
|
1821 | |
|
|
1822 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1823 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1824 | successfully read or write some data. If you go into an idle state where |
|
|
1825 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1826 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1827 | |
|
|
1828 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1829 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1830 | member and C<ev_timer_again>. |
|
|
1831 | |
|
|
1832 | At start: |
|
|
1833 | |
|
|
1834 | ev_init (timer, callback); |
|
|
1835 | timer->repeat = 60.; |
|
|
1836 | ev_timer_again (loop, timer); |
|
|
1837 | |
|
|
1838 | Each time there is some activity: |
|
|
1839 | |
|
|
1840 | ev_timer_again (loop, timer); |
|
|
1841 | |
|
|
1842 | It is even possible to change the time-out on the fly, regardless of |
|
|
1843 | whether the watcher is active or not: |
|
|
1844 | |
|
|
1845 | timer->repeat = 30.; |
|
|
1846 | ev_timer_again (loop, timer); |
|
|
1847 | |
|
|
1848 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1849 | you want to modify its timeout value, as libev does not have to completely |
|
|
1850 | remove and re-insert the timer from/into its internal data structure. |
|
|
1851 | |
|
|
1852 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1853 | |
|
|
1854 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1855 | |
|
|
1856 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1857 | relatively long compared to the intervals between other activity - in |
|
|
1858 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1859 | associated activity resets. |
|
|
1860 | |
|
|
1861 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1862 | but remember the time of last activity, and check for a real timeout only |
|
|
1863 | within the callback: |
|
|
1864 | |
|
|
1865 | ev_tstamp timeout = 60.; |
|
|
1866 | ev_tstamp last_activity; // time of last activity |
|
|
1867 | ev_timer timer; |
|
|
1868 | |
|
|
1869 | static void |
|
|
1870 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1871 | { |
|
|
1872 | // calculate when the timeout would happen |
|
|
1873 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
|
|
1874 | |
|
|
1875 | // if negative, it means we the timeout already occured |
|
|
1876 | if (after < 0.) |
|
|
1877 | { |
|
|
1878 | // timeout occurred, take action |
|
|
1879 | } |
|
|
1880 | else |
|
|
1881 | { |
|
|
1882 | // callback was invoked, but there was some recent |
|
|
1883 | // activity. simply restart the timer to time out |
|
|
1884 | // after "after" seconds, which is the earliest time |
|
|
1885 | // the timeout can occur. |
|
|
1886 | ev_timer_set (w, after, 0.); |
|
|
1887 | ev_timer_start (EV_A_ w); |
|
|
1888 | } |
|
|
1889 | } |
|
|
1890 | |
|
|
1891 | To summarise the callback: first calculate in how many seconds the |
|
|
1892 | timeout will occur (by calculating the absolute time when it would occur, |
|
|
1893 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
|
|
1894 | (EV_A)> from that). |
|
|
1895 | |
|
|
1896 | If this value is negative, then we are already past the timeout, i.e. we |
|
|
1897 | timed out, and need to do whatever is needed in this case. |
|
|
1898 | |
|
|
1899 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1900 | and simply start the timer with this timeout value. |
|
|
1901 | |
|
|
1902 | In other words, each time the callback is invoked it will check whether |
|
|
1903 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1904 | again at the earliest time it could time out. Rinse. Repeat. |
|
|
1905 | |
|
|
1906 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1907 | minus half the average time between activity), but virtually no calls to |
|
|
1908 | libev to change the timeout. |
|
|
1909 | |
|
|
1910 | To start the machinery, simply initialise the watcher and set |
|
|
1911 | C<last_activity> to the current time (meaning there was some activity just |
|
|
1912 | now), then call the callback, which will "do the right thing" and start |
|
|
1913 | the timer: |
|
|
1914 | |
|
|
1915 | last_activity = ev_now (EV_A); |
|
|
1916 | ev_init (&timer, callback); |
|
|
1917 | callback (EV_A_ &timer, 0); |
|
|
1918 | |
|
|
1919 | When there is some activity, simply store the current time in |
|
|
1920 | C<last_activity>, no libev calls at all: |
|
|
1921 | |
|
|
1922 | if (activity detected) |
|
|
1923 | last_activity = ev_now (EV_A); |
|
|
1924 | |
|
|
1925 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1926 | providing a new value, stopping the timer and calling the callback, which |
|
|
1927 | will agaion do the right thing (for example, time out immediately :). |
|
|
1928 | |
|
|
1929 | timeout = new_value; |
|
|
1930 | ev_timer_stop (EV_A_ &timer); |
|
|
1931 | callback (EV_A_ &timer, 0); |
|
|
1932 | |
|
|
1933 | This technique is slightly more complex, but in most cases where the |
|
|
1934 | time-out is unlikely to be triggered, much more efficient. |
|
|
1935 | |
|
|
1936 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1937 | |
|
|
1938 | If there is not one request, but many thousands (millions...), all |
|
|
1939 | employing some kind of timeout with the same timeout value, then one can |
|
|
1940 | do even better: |
|
|
1941 | |
|
|
1942 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1943 | at the I<end> of the list. |
|
|
1944 | |
|
|
1945 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1946 | the list is expected to fire (for example, using the technique #3). |
|
|
1947 | |
|
|
1948 | When there is some activity, remove the timer from the list, recalculate |
|
|
1949 | the timeout, append it to the end of the list again, and make sure to |
|
|
1950 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1951 | |
|
|
1952 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1953 | starting, stopping and updating the timers, at the expense of a major |
|
|
1954 | complication, and having to use a constant timeout. The constant timeout |
|
|
1955 | ensures that the list stays sorted. |
|
|
1956 | |
|
|
1957 | =back |
|
|
1958 | |
|
|
1959 | So which method the best? |
|
|
1960 | |
|
|
1961 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1962 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1963 | better, and isn't very complicated either. In most case, choosing either |
|
|
1964 | one is fine, with #3 being better in typical situations. |
|
|
1965 | |
|
|
1966 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1967 | rather complicated, but extremely efficient, something that really pays |
|
|
1968 | off after the first million or so of active timers, i.e. it's usually |
|
|
1969 | overkill :) |
|
|
1970 | |
|
|
1971 | =head3 The special problem of being too early |
|
|
1972 | |
|
|
1973 | If you ask a timer to call your callback after three seconds, then |
|
|
1974 | you expect it to be invoked after three seconds - but of course, this |
|
|
1975 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1976 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1977 | process with a STOP signal for a few hours for example. |
|
|
1978 | |
|
|
1979 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1980 | delay has occurred, but cannot guarantee this. |
|
|
1981 | |
|
|
1982 | A less obvious failure mode is calling your callback too early: many event |
|
|
1983 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1984 | this can cause your callback to be invoked much earlier than you would |
|
|
1985 | expect. |
|
|
1986 | |
|
|
1987 | To see why, imagine a system with a clock that only offers full second |
|
|
1988 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1989 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1990 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1991 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1992 | |
|
|
1993 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1994 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1995 | one-second delay was requested - this is being "too early", despite best |
|
|
1996 | intentions. |
|
|
1997 | |
|
|
1998 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1999 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2000 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2001 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2002 | |
|
|
2003 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2004 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2005 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2006 | late" side of things. |
|
|
2007 | |
|
|
2008 | =head3 The special problem of time updates |
|
|
2009 | |
|
|
2010 | Establishing the current time is a costly operation (it usually takes |
|
|
2011 | at least one system call): EV therefore updates its idea of the current |
|
|
2012 | time only before and after C<ev_run> collects new events, which causes a |
|
|
2013 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
2014 | lots of events in one iteration. |
1144 | |
2015 | |
1145 | The relative timeouts are calculated relative to the C<ev_now ()> |
2016 | The relative timeouts are calculated relative to the C<ev_now ()> |
1146 | time. This is usually the right thing as this timestamp refers to the time |
2017 | time. This is usually the right thing as this timestamp refers to the time |
1147 | of the event triggering whatever timeout you are modifying/starting. If |
2018 | of the event triggering whatever timeout you are modifying/starting. If |
1148 | you suspect event processing to be delayed and you I<need> to base the timeout |
2019 | you suspect event processing to be delayed and you I<need> to base the |
1149 | on the current time, use something like this to adjust for this: |
2020 | timeout on the current time, use something like this to adjust for this: |
1150 | |
2021 | |
1151 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2022 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1152 | |
2023 | |
1153 | The callback is guarenteed to be invoked only when its timeout has passed, |
2024 | If the event loop is suspended for a long time, you can also force an |
1154 | but if multiple timers become ready during the same loop iteration then |
2025 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1155 | order of execution is undefined. |
2026 | ()>. |
|
|
2027 | |
|
|
2028 | =head3 The special problem of unsynchronised clocks |
|
|
2029 | |
|
|
2030 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2031 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2032 | jumps). |
|
|
2033 | |
|
|
2034 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2035 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2036 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2037 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2038 | than a directly following call to C<time>. |
|
|
2039 | |
|
|
2040 | The moral of this is to only compare libev-related timestamps with |
|
|
2041 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2042 | a second or so. |
|
|
2043 | |
|
|
2044 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2045 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2046 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2047 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2048 | |
|
|
2049 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2050 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2051 | I<measured according to the real time>, not the system clock. |
|
|
2052 | |
|
|
2053 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2054 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2055 | exactly the right behaviour. |
|
|
2056 | |
|
|
2057 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2058 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2059 | time, where your comparisons will always generate correct results. |
|
|
2060 | |
|
|
2061 | =head3 The special problems of suspended animation |
|
|
2062 | |
|
|
2063 | When you leave the server world it is quite customary to hit machines that |
|
|
2064 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2065 | |
|
|
2066 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2067 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2068 | to run until the system is suspended, but they will not advance while the |
|
|
2069 | system is suspended. That means, on resume, it will be as if the program |
|
|
2070 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2071 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2072 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2073 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2074 | be adjusted accordingly. |
|
|
2075 | |
|
|
2076 | I would not be surprised to see different behaviour in different between |
|
|
2077 | operating systems, OS versions or even different hardware. |
|
|
2078 | |
|
|
2079 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2080 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2081 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2082 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2083 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2084 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2085 | |
|
|
2086 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2087 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2088 | deterministic behaviour in this case (you can do nothing against |
|
|
2089 | C<SIGSTOP>). |
1156 | |
2090 | |
1157 | =head3 Watcher-Specific Functions and Data Members |
2091 | =head3 Watcher-Specific Functions and Data Members |
1158 | |
2092 | |
1159 | =over 4 |
2093 | =over 4 |
1160 | |
2094 | |
1161 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2095 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1162 | |
2096 | |
1163 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2097 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1164 | |
2098 | |
1165 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
2099 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1166 | C<0.>, then it will automatically be stopped. If it is positive, then the |
2100 | is C<0.>, then it will automatically be stopped once the timeout is |
1167 | timer will automatically be configured to trigger again C<repeat> seconds |
2101 | reached. If it is positive, then the timer will automatically be |
1168 | later, again, and again, until stopped manually. |
2102 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
2103 | until stopped manually. |
1169 | |
2104 | |
1170 | The timer itself will do a best-effort at avoiding drift, that is, if you |
2105 | The timer itself will do a best-effort at avoiding drift, that is, if |
1171 | configure a timer to trigger every 10 seconds, then it will trigger at |
2106 | you configure a timer to trigger every 10 seconds, then it will normally |
1172 | exactly 10 second intervals. If, however, your program cannot keep up with |
2107 | trigger at exactly 10 second intervals. If, however, your program cannot |
1173 | the timer (because it takes longer than those 10 seconds to do stuff) the |
2108 | keep up with the timer (because it takes longer than those 10 seconds to |
1174 | timer will not fire more than once per event loop iteration. |
2109 | do stuff) the timer will not fire more than once per event loop iteration. |
1175 | |
2110 | |
1176 | =item ev_timer_again (loop, ev_timer *) |
2111 | =item ev_timer_again (loop, ev_timer *) |
1177 | |
2112 | |
1178 | This will act as if the timer timed out and restart it again if it is |
2113 | This will act as if the timer timed out, and restarts it again if it is |
1179 | repeating. The exact semantics are: |
2114 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2115 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1180 | |
2116 | |
|
|
2117 | The exact semantics are as in the following rules, all of which will be |
|
|
2118 | applied to the watcher: |
|
|
2119 | |
|
|
2120 | =over 4 |
|
|
2121 | |
1181 | If the timer is pending, its pending status is cleared. |
2122 | =item If the timer is pending, the pending status is always cleared. |
1182 | |
2123 | |
1183 | If the timer is started but nonrepeating, stop it (as if it timed out). |
2124 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2125 | out, without invoking it). |
1184 | |
2126 | |
1185 | If the timer is repeating, either start it if necessary (with the |
2127 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1186 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2128 | and start the timer, if necessary. |
1187 | |
2129 | |
1188 | This sounds a bit complicated, but here is a useful and typical |
2130 | =back |
1189 | example: Imagine you have a tcp connection and you want a so-called idle |
|
|
1190 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1191 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1192 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1193 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1194 | you go into an idle state where you do not expect data to travel on the |
|
|
1195 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1196 | automatically restart it if need be. |
|
|
1197 | |
2131 | |
1198 | That means you can ignore the C<after> value and C<ev_timer_start> |
2132 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1199 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
2133 | usage example. |
1200 | |
2134 | |
1201 | ev_timer_init (timer, callback, 0., 5.); |
2135 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1202 | ev_timer_again (loop, timer); |
|
|
1203 | ... |
|
|
1204 | timer->again = 17.; |
|
|
1205 | ev_timer_again (loop, timer); |
|
|
1206 | ... |
|
|
1207 | timer->again = 10.; |
|
|
1208 | ev_timer_again (loop, timer); |
|
|
1209 | |
2136 | |
1210 | This is more slightly efficient then stopping/starting the timer each time |
2137 | Returns the remaining time until a timer fires. If the timer is active, |
1211 | you want to modify its timeout value. |
2138 | then this time is relative to the current event loop time, otherwise it's |
|
|
2139 | the timeout value currently configured. |
|
|
2140 | |
|
|
2141 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2142 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2143 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2144 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2145 | too), and so on. |
1212 | |
2146 | |
1213 | =item ev_tstamp repeat [read-write] |
2147 | =item ev_tstamp repeat [read-write] |
1214 | |
2148 | |
1215 | The current C<repeat> value. Will be used each time the watcher times out |
2149 | The current C<repeat> value. Will be used each time the watcher times out |
1216 | or C<ev_timer_again> is called and determines the next timeout (if any), |
2150 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1217 | which is also when any modifications are taken into account. |
2151 | which is also when any modifications are taken into account. |
1218 | |
2152 | |
1219 | =back |
2153 | =back |
1220 | |
2154 | |
1221 | =head3 Examples |
2155 | =head3 Examples |
1222 | |
2156 | |
1223 | Example: Create a timer that fires after 60 seconds. |
2157 | Example: Create a timer that fires after 60 seconds. |
1224 | |
2158 | |
1225 | static void |
2159 | static void |
1226 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2160 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1227 | { |
2161 | { |
1228 | .. one minute over, w is actually stopped right here |
2162 | .. one minute over, w is actually stopped right here |
1229 | } |
2163 | } |
1230 | |
2164 | |
1231 | struct ev_timer mytimer; |
2165 | ev_timer mytimer; |
1232 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2166 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1233 | ev_timer_start (loop, &mytimer); |
2167 | ev_timer_start (loop, &mytimer); |
1234 | |
2168 | |
1235 | Example: Create a timeout timer that times out after 10 seconds of |
2169 | Example: Create a timeout timer that times out after 10 seconds of |
1236 | inactivity. |
2170 | inactivity. |
1237 | |
2171 | |
1238 | static void |
2172 | static void |
1239 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2173 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1240 | { |
2174 | { |
1241 | .. ten seconds without any activity |
2175 | .. ten seconds without any activity |
1242 | } |
2176 | } |
1243 | |
2177 | |
1244 | struct ev_timer mytimer; |
2178 | ev_timer mytimer; |
1245 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2179 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1246 | ev_timer_again (&mytimer); /* start timer */ |
2180 | ev_timer_again (&mytimer); /* start timer */ |
1247 | ev_loop (loop, 0); |
2181 | ev_run (loop, 0); |
1248 | |
2182 | |
1249 | // and in some piece of code that gets executed on any "activity": |
2183 | // and in some piece of code that gets executed on any "activity": |
1250 | // reset the timeout to start ticking again at 10 seconds |
2184 | // reset the timeout to start ticking again at 10 seconds |
1251 | ev_timer_again (&mytimer); |
2185 | ev_timer_again (&mytimer); |
1252 | |
2186 | |
1253 | |
2187 | |
1254 | =head2 C<ev_periodic> - to cron or not to cron? |
2188 | =head2 C<ev_periodic> - to cron or not to cron? |
1255 | |
2189 | |
1256 | Periodic watchers are also timers of a kind, but they are very versatile |
2190 | Periodic watchers are also timers of a kind, but they are very versatile |
1257 | (and unfortunately a bit complex). |
2191 | (and unfortunately a bit complex). |
1258 | |
2192 | |
1259 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2193 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1260 | but on wallclock time (absolute time). You can tell a periodic watcher |
2194 | relative time, the physical time that passes) but on wall clock time |
1261 | to trigger "at" some specific point in time. For example, if you tell a |
2195 | (absolute time, the thing you can read on your calender or clock). The |
1262 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
2196 | difference is that wall clock time can run faster or slower than real |
1263 | + 10.>) and then reset your system clock to the last year, then it will |
2197 | time, and time jumps are not uncommon (e.g. when you adjust your |
1264 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
2198 | wrist-watch). |
1265 | roughly 10 seconds later). |
|
|
1266 | |
2199 | |
1267 | They can also be used to implement vastly more complex timers, such as |
2200 | You can tell a periodic watcher to trigger after some specific point |
1268 | triggering an event on each midnight, local time or other, complicated, |
2201 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
1269 | rules. |
2202 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2203 | not a delay) and then reset your system clock to January of the previous |
|
|
2204 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2205 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2206 | it, as it uses a relative timeout). |
1270 | |
2207 | |
|
|
2208 | C<ev_periodic> watchers can also be used to implement vastly more complex |
|
|
2209 | timers, such as triggering an event on each "midnight, local time", or |
|
|
2210 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2211 | those cannot react to time jumps. |
|
|
2212 | |
1271 | As with timers, the callback is guarenteed to be invoked only when the |
2213 | As with timers, the callback is guaranteed to be invoked only when the |
1272 | time (C<at>) has been passed, but if multiple periodic timers become ready |
2214 | point in time where it is supposed to trigger has passed. If multiple |
1273 | during the same loop iteration then order of execution is undefined. |
2215 | timers become ready during the same loop iteration then the ones with |
|
|
2216 | earlier time-out values are invoked before ones with later time-out values |
|
|
2217 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1274 | |
2218 | |
1275 | =head3 Watcher-Specific Functions and Data Members |
2219 | =head3 Watcher-Specific Functions and Data Members |
1276 | |
2220 | |
1277 | =over 4 |
2221 | =over 4 |
1278 | |
2222 | |
1279 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2223 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1280 | |
2224 | |
1281 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2225 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1282 | |
2226 | |
1283 | Lots of arguments, lets sort it out... There are basically three modes of |
2227 | Lots of arguments, let's sort it out... There are basically three modes of |
1284 | operation, and we will explain them from simplest to complex: |
2228 | operation, and we will explain them from simplest to most complex: |
1285 | |
2229 | |
1286 | =over 4 |
2230 | =over 4 |
1287 | |
2231 | |
1288 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2232 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1289 | |
2233 | |
1290 | In this configuration the watcher triggers an event at the wallclock time |
2234 | In this configuration the watcher triggers an event after the wall clock |
1291 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
2235 | time C<offset> has passed. It will not repeat and will not adjust when a |
1292 | that is, if it is to be run at January 1st 2011 then it will run when the |
2236 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1293 | system time reaches or surpasses this time. |
2237 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2238 | this point in time. |
1294 | |
2239 | |
1295 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2240 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1296 | |
2241 | |
1297 | In this mode the watcher will always be scheduled to time out at the next |
2242 | In this mode the watcher will always be scheduled to time out at the next |
1298 | C<at + N * interval> time (for some integer N, which can also be negative) |
2243 | C<offset + N * interval> time (for some integer N, which can also be |
1299 | and then repeat, regardless of any time jumps. |
2244 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2245 | argument is merely an offset into the C<interval> periods. |
1300 | |
2246 | |
1301 | This can be used to create timers that do not drift with respect to system |
2247 | This can be used to create timers that do not drift with respect to the |
1302 | time: |
2248 | system clock, for example, here is an C<ev_periodic> that triggers each |
|
|
2249 | hour, on the hour (with respect to UTC): |
1303 | |
2250 | |
1304 | ev_periodic_set (&periodic, 0., 3600., 0); |
2251 | ev_periodic_set (&periodic, 0., 3600., 0); |
1305 | |
2252 | |
1306 | This doesn't mean there will always be 3600 seconds in between triggers, |
2253 | This doesn't mean there will always be 3600 seconds in between triggers, |
1307 | but only that the the callback will be called when the system time shows a |
2254 | but only that the callback will be called when the system time shows a |
1308 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2255 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1309 | by 3600. |
2256 | by 3600. |
1310 | |
2257 | |
1311 | Another way to think about it (for the mathematically inclined) is that |
2258 | Another way to think about it (for the mathematically inclined) is that |
1312 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2259 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1313 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2260 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1314 | |
2261 | |
1315 | For numerical stability it is preferable that the C<at> value is near |
2262 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1316 | C<ev_now ()> (the current time), but there is no range requirement for |
2263 | interval value should be higher than C<1/8192> (which is around 100 |
1317 | this value. |
2264 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2265 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2266 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2267 | C<0> and C<interval>, which is also the recommended range. |
1318 | |
2268 | |
|
|
2269 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
2270 | speed for example), so if C<interval> is very small then timing stability |
|
|
2271 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
2272 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
2273 | |
1319 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2274 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1320 | |
2275 | |
1321 | In this mode the values for C<interval> and C<at> are both being |
2276 | In this mode the values for C<interval> and C<offset> are both being |
1322 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2277 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1323 | reschedule callback will be called with the watcher as first, and the |
2278 | reschedule callback will be called with the watcher as first, and the |
1324 | current time as second argument. |
2279 | current time as second argument. |
1325 | |
2280 | |
1326 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2281 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1327 | ever, or make any event loop modifications>. If you need to stop it, |
2282 | or make ANY other event loop modifications whatsoever, unless explicitly |
1328 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
2283 | allowed by documentation here>. |
1329 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1330 | |
2284 | |
|
|
2285 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
2286 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
2287 | only event loop modification you are allowed to do). |
|
|
2288 | |
1331 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
2289 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1332 | ev_tstamp now)>, e.g.: |
2290 | *w, ev_tstamp now)>, e.g.: |
1333 | |
2291 | |
|
|
2292 | static ev_tstamp |
1334 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2293 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1335 | { |
2294 | { |
1336 | return now + 60.; |
2295 | return now + 60.; |
1337 | } |
2296 | } |
1338 | |
2297 | |
1339 | It must return the next time to trigger, based on the passed time value |
2298 | It must return the next time to trigger, based on the passed time value |
1340 | (that is, the lowest time value larger than to the second argument). It |
2299 | (that is, the lowest time value larger than to the second argument). It |
1341 | will usually be called just before the callback will be triggered, but |
2300 | will usually be called just before the callback will be triggered, but |
1342 | might be called at other times, too. |
2301 | might be called at other times, too. |
1343 | |
2302 | |
1344 | NOTE: I<< This callback must always return a time that is later than the |
2303 | NOTE: I<< This callback must always return a time that is higher than or |
1345 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
2304 | equal to the passed C<now> value >>. |
1346 | |
2305 | |
1347 | This can be used to create very complex timers, such as a timer that |
2306 | This can be used to create very complex timers, such as a timer that |
1348 | triggers on each midnight, local time. To do this, you would calculate the |
2307 | triggers on "next midnight, local time". To do this, you would calculate the |
1349 | next midnight after C<now> and return the timestamp value for this. How |
2308 | next midnight after C<now> and return the timestamp value for this. How |
1350 | you do this is, again, up to you (but it is not trivial, which is the main |
2309 | you do this is, again, up to you (but it is not trivial, which is the main |
1351 | reason I omitted it as an example). |
2310 | reason I omitted it as an example). |
1352 | |
2311 | |
1353 | =back |
2312 | =back |
… | |
… | |
1357 | Simply stops and restarts the periodic watcher again. This is only useful |
2316 | Simply stops and restarts the periodic watcher again. This is only useful |
1358 | when you changed some parameters or the reschedule callback would return |
2317 | when you changed some parameters or the reschedule callback would return |
1359 | a different time than the last time it was called (e.g. in a crond like |
2318 | a different time than the last time it was called (e.g. in a crond like |
1360 | program when the crontabs have changed). |
2319 | program when the crontabs have changed). |
1361 | |
2320 | |
|
|
2321 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
2322 | |
|
|
2323 | When active, returns the absolute time that the watcher is supposed |
|
|
2324 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2325 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2326 | rescheduling modes. |
|
|
2327 | |
1362 | =item ev_tstamp offset [read-write] |
2328 | =item ev_tstamp offset [read-write] |
1363 | |
2329 | |
1364 | When repeating, this contains the offset value, otherwise this is the |
2330 | When repeating, this contains the offset value, otherwise this is the |
1365 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2331 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2332 | although libev might modify this value for better numerical stability). |
1366 | |
2333 | |
1367 | Can be modified any time, but changes only take effect when the periodic |
2334 | Can be modified any time, but changes only take effect when the periodic |
1368 | timer fires or C<ev_periodic_again> is being called. |
2335 | timer fires or C<ev_periodic_again> is being called. |
1369 | |
2336 | |
1370 | =item ev_tstamp interval [read-write] |
2337 | =item ev_tstamp interval [read-write] |
1371 | |
2338 | |
1372 | The current interval value. Can be modified any time, but changes only |
2339 | The current interval value. Can be modified any time, but changes only |
1373 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2340 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1374 | called. |
2341 | called. |
1375 | |
2342 | |
1376 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2343 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1377 | |
2344 | |
1378 | The current reschedule callback, or C<0>, if this functionality is |
2345 | The current reschedule callback, or C<0>, if this functionality is |
1379 | switched off. Can be changed any time, but changes only take effect when |
2346 | switched off. Can be changed any time, but changes only take effect when |
1380 | the periodic timer fires or C<ev_periodic_again> is being called. |
2347 | the periodic timer fires or C<ev_periodic_again> is being called. |
1381 | |
2348 | |
1382 | =item ev_tstamp at [read-only] |
|
|
1383 | |
|
|
1384 | When active, contains the absolute time that the watcher is supposed to |
|
|
1385 | trigger next. |
|
|
1386 | |
|
|
1387 | =back |
2349 | =back |
1388 | |
2350 | |
1389 | =head3 Examples |
2351 | =head3 Examples |
1390 | |
2352 | |
1391 | Example: Call a callback every hour, or, more precisely, whenever the |
2353 | Example: Call a callback every hour, or, more precisely, whenever the |
1392 | system clock is divisible by 3600. The callback invocation times have |
2354 | system time is divisible by 3600. The callback invocation times have |
1393 | potentially a lot of jittering, but good long-term stability. |
2355 | potentially a lot of jitter, but good long-term stability. |
1394 | |
2356 | |
1395 | static void |
2357 | static void |
1396 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2358 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1397 | { |
2359 | { |
1398 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2360 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1399 | } |
2361 | } |
1400 | |
2362 | |
1401 | struct ev_periodic hourly_tick; |
2363 | ev_periodic hourly_tick; |
1402 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2364 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1403 | ev_periodic_start (loop, &hourly_tick); |
2365 | ev_periodic_start (loop, &hourly_tick); |
1404 | |
2366 | |
1405 | Example: The same as above, but use a reschedule callback to do it: |
2367 | Example: The same as above, but use a reschedule callback to do it: |
1406 | |
2368 | |
1407 | #include <math.h> |
2369 | #include <math.h> |
1408 | |
2370 | |
1409 | static ev_tstamp |
2371 | static ev_tstamp |
1410 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2372 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1411 | { |
2373 | { |
1412 | return fmod (now, 3600.) + 3600.; |
2374 | return now + (3600. - fmod (now, 3600.)); |
1413 | } |
2375 | } |
1414 | |
2376 | |
1415 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2377 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1416 | |
2378 | |
1417 | Example: Call a callback every hour, starting now: |
2379 | Example: Call a callback every hour, starting now: |
1418 | |
2380 | |
1419 | struct ev_periodic hourly_tick; |
2381 | ev_periodic hourly_tick; |
1420 | ev_periodic_init (&hourly_tick, clock_cb, |
2382 | ev_periodic_init (&hourly_tick, clock_cb, |
1421 | fmod (ev_now (loop), 3600.), 3600., 0); |
2383 | fmod (ev_now (loop), 3600.), 3600., 0); |
1422 | ev_periodic_start (loop, &hourly_tick); |
2384 | ev_periodic_start (loop, &hourly_tick); |
1423 | |
2385 | |
1424 | |
2386 | |
1425 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2387 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1426 | |
2388 | |
1427 | Signal watchers will trigger an event when the process receives a specific |
2389 | Signal watchers will trigger an event when the process receives a specific |
1428 | signal one or more times. Even though signals are very asynchronous, libev |
2390 | signal one or more times. Even though signals are very asynchronous, libev |
1429 | will try it's best to deliver signals synchronously, i.e. as part of the |
2391 | will try its best to deliver signals synchronously, i.e. as part of the |
1430 | normal event processing, like any other event. |
2392 | normal event processing, like any other event. |
1431 | |
2393 | |
|
|
2394 | If you want signals to be delivered truly asynchronously, just use |
|
|
2395 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2396 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2397 | synchronously wake up an event loop. |
|
|
2398 | |
1432 | You can configure as many watchers as you like per signal. Only when the |
2399 | You can configure as many watchers as you like for the same signal, but |
|
|
2400 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2401 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2402 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2403 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2404 | |
1433 | first watcher gets started will libev actually register a signal watcher |
2405 | When the first watcher gets started will libev actually register something |
1434 | with the kernel (thus it coexists with your own signal handlers as long |
2406 | with the kernel (thus it coexists with your own signal handlers as long as |
1435 | as you don't register any with libev). Similarly, when the last signal |
2407 | you don't register any with libev for the same signal). |
1436 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1437 | SIG_DFL (regardless of what it was set to before). |
|
|
1438 | |
2408 | |
1439 | If possible and supported, libev will install its handlers with |
2409 | If possible and supported, libev will install its handlers with |
1440 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
2410 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1441 | interrupted. If you have a problem with syscalls getting interrupted by |
2411 | not be unduly interrupted. If you have a problem with system calls getting |
1442 | signals you can block all signals in an C<ev_check> watcher and unblock |
2412 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1443 | them in an C<ev_prepare> watcher. |
2413 | and unblock them in an C<ev_prepare> watcher. |
|
|
2414 | |
|
|
2415 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2416 | |
|
|
2417 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2418 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2419 | stopping it again), that is, libev might or might not block the signal, |
|
|
2420 | and might or might not set or restore the installed signal handler (but |
|
|
2421 | see C<EVFLAG_NOSIGMASK>). |
|
|
2422 | |
|
|
2423 | While this does not matter for the signal disposition (libev never |
|
|
2424 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2425 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2426 | certain signals to be blocked. |
|
|
2427 | |
|
|
2428 | This means that before calling C<exec> (from the child) you should reset |
|
|
2429 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2430 | choice usually). |
|
|
2431 | |
|
|
2432 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2433 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2434 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2435 | |
|
|
2436 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2437 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2438 | the window of opportunity for problems, it will not go away, as libev |
|
|
2439 | I<has> to modify the signal mask, at least temporarily. |
|
|
2440 | |
|
|
2441 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2442 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2443 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2444 | |
|
|
2445 | =head3 The special problem of threads signal handling |
|
|
2446 | |
|
|
2447 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2448 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2449 | threads in a process block signals, which is hard to achieve. |
|
|
2450 | |
|
|
2451 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2452 | for the same signals), you can tackle this problem by globally blocking |
|
|
2453 | all signals before creating any threads (or creating them with a fully set |
|
|
2454 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2455 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2456 | these signals. You can pass on any signals that libev might be interested |
|
|
2457 | in by calling C<ev_feed_signal>. |
1444 | |
2458 | |
1445 | =head3 Watcher-Specific Functions and Data Members |
2459 | =head3 Watcher-Specific Functions and Data Members |
1446 | |
2460 | |
1447 | =over 4 |
2461 | =over 4 |
1448 | |
2462 | |
… | |
… | |
1459 | |
2473 | |
1460 | =back |
2474 | =back |
1461 | |
2475 | |
1462 | =head3 Examples |
2476 | =head3 Examples |
1463 | |
2477 | |
1464 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2478 | Example: Try to exit cleanly on SIGINT. |
1465 | |
2479 | |
1466 | static void |
2480 | static void |
1467 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2481 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1468 | { |
2482 | { |
1469 | ev_unloop (loop, EVUNLOOP_ALL); |
2483 | ev_break (loop, EVBREAK_ALL); |
1470 | } |
2484 | } |
1471 | |
2485 | |
1472 | struct ev_signal signal_watcher; |
2486 | ev_signal signal_watcher; |
1473 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2487 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1474 | ev_signal_start (loop, &sigint_cb); |
2488 | ev_signal_start (loop, &signal_watcher); |
1475 | |
2489 | |
1476 | |
2490 | |
1477 | =head2 C<ev_child> - watch out for process status changes |
2491 | =head2 C<ev_child> - watch out for process status changes |
1478 | |
2492 | |
1479 | Child watchers trigger when your process receives a SIGCHLD in response to |
2493 | Child watchers trigger when your process receives a SIGCHLD in response to |
1480 | some child status changes (most typically when a child of yours dies). It |
2494 | some child status changes (most typically when a child of yours dies or |
1481 | is permissible to install a child watcher I<after> the child has been |
2495 | exits). It is permissible to install a child watcher I<after> the child |
1482 | forked (which implies it might have already exited), as long as the event |
2496 | has been forked (which implies it might have already exited), as long |
1483 | loop isn't entered (or is continued from a watcher). |
2497 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2498 | forking and then immediately registering a watcher for the child is fine, |
|
|
2499 | but forking and registering a watcher a few event loop iterations later or |
|
|
2500 | in the next callback invocation is not. |
1484 | |
2501 | |
1485 | Only the default event loop is capable of handling signals, and therefore |
2502 | Only the default event loop is capable of handling signals, and therefore |
1486 | you can only rgeister child watchers in the default event loop. |
2503 | you can only register child watchers in the default event loop. |
|
|
2504 | |
|
|
2505 | Due to some design glitches inside libev, child watchers will always be |
|
|
2506 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2507 | libev) |
1487 | |
2508 | |
1488 | =head3 Process Interaction |
2509 | =head3 Process Interaction |
1489 | |
2510 | |
1490 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2511 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1491 | initialised. This is necessary to guarantee proper behaviour even if |
2512 | initialised. This is necessary to guarantee proper behaviour even if the |
1492 | the first child watcher is started after the child exits. The occurance |
2513 | first child watcher is started after the child exits. The occurrence |
1493 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2514 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1494 | synchronously as part of the event loop processing. Libev always reaps all |
2515 | synchronously as part of the event loop processing. Libev always reaps all |
1495 | children, even ones not watched. |
2516 | children, even ones not watched. |
1496 | |
2517 | |
1497 | =head3 Overriding the Built-In Processing |
2518 | =head3 Overriding the Built-In Processing |
… | |
… | |
1501 | handler, you can override it easily by installing your own handler for |
2522 | handler, you can override it easily by installing your own handler for |
1502 | C<SIGCHLD> after initialising the default loop, and making sure the |
2523 | C<SIGCHLD> after initialising the default loop, and making sure the |
1503 | default loop never gets destroyed. You are encouraged, however, to use an |
2524 | default loop never gets destroyed. You are encouraged, however, to use an |
1504 | event-based approach to child reaping and thus use libev's support for |
2525 | event-based approach to child reaping and thus use libev's support for |
1505 | that, so other libev users can use C<ev_child> watchers freely. |
2526 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2527 | |
|
|
2528 | =head3 Stopping the Child Watcher |
|
|
2529 | |
|
|
2530 | Currently, the child watcher never gets stopped, even when the |
|
|
2531 | child terminates, so normally one needs to stop the watcher in the |
|
|
2532 | callback. Future versions of libev might stop the watcher automatically |
|
|
2533 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2534 | problem). |
1506 | |
2535 | |
1507 | =head3 Watcher-Specific Functions and Data Members |
2536 | =head3 Watcher-Specific Functions and Data Members |
1508 | |
2537 | |
1509 | =over 4 |
2538 | =over 4 |
1510 | |
2539 | |
… | |
… | |
1539 | =head3 Examples |
2568 | =head3 Examples |
1540 | |
2569 | |
1541 | Example: C<fork()> a new process and install a child handler to wait for |
2570 | Example: C<fork()> a new process and install a child handler to wait for |
1542 | its completion. |
2571 | its completion. |
1543 | |
2572 | |
1544 | ev_child cw; |
2573 | ev_child cw; |
1545 | |
2574 | |
1546 | static void |
2575 | static void |
1547 | child_cb (EV_P_ struct ev_child *w, int revents) |
2576 | child_cb (EV_P_ ev_child *w, int revents) |
1548 | { |
2577 | { |
1549 | ev_child_stop (EV_A_ w); |
2578 | ev_child_stop (EV_A_ w); |
1550 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2579 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1551 | } |
2580 | } |
1552 | |
2581 | |
1553 | pid_t pid = fork (); |
2582 | pid_t pid = fork (); |
1554 | |
2583 | |
1555 | if (pid < 0) |
2584 | if (pid < 0) |
1556 | // error |
2585 | // error |
1557 | else if (pid == 0) |
2586 | else if (pid == 0) |
1558 | { |
2587 | { |
1559 | // the forked child executes here |
2588 | // the forked child executes here |
1560 | exit (1); |
2589 | exit (1); |
1561 | } |
2590 | } |
1562 | else |
2591 | else |
1563 | { |
2592 | { |
1564 | ev_child_init (&cw, child_cb, pid, 0); |
2593 | ev_child_init (&cw, child_cb, pid, 0); |
1565 | ev_child_start (EV_DEFAULT_ &cw); |
2594 | ev_child_start (EV_DEFAULT_ &cw); |
1566 | } |
2595 | } |
1567 | |
2596 | |
1568 | |
2597 | |
1569 | =head2 C<ev_stat> - did the file attributes just change? |
2598 | =head2 C<ev_stat> - did the file attributes just change? |
1570 | |
2599 | |
1571 | This watches a filesystem path for attribute changes. That is, it calls |
2600 | This watches a file system path for attribute changes. That is, it calls |
1572 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2601 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1573 | compared to the last time, invoking the callback if it did. |
2602 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2603 | it did. |
1574 | |
2604 | |
1575 | The path does not need to exist: changing from "path exists" to "path does |
2605 | The path does not need to exist: changing from "path exists" to "path does |
1576 | not exist" is a status change like any other. The condition "path does |
2606 | not exist" is a status change like any other. The condition "path does not |
1577 | not exist" is signified by the C<st_nlink> field being zero (which is |
2607 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1578 | otherwise always forced to be at least one) and all the other fields of |
2608 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1579 | the stat buffer having unspecified contents. |
2609 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2610 | contents. |
1580 | |
2611 | |
1581 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2612 | The path I<must not> end in a slash or contain special components such as |
|
|
2613 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1582 | relative and your working directory changes, the behaviour is undefined. |
2614 | your working directory changes, then the behaviour is undefined. |
1583 | |
2615 | |
1584 | Since there is no standard to do this, the portable implementation simply |
2616 | Since there is no portable change notification interface available, the |
1585 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2617 | portable implementation simply calls C<stat(2)> regularly on the path |
1586 | can specify a recommended polling interval for this case. If you specify |
2618 | to see if it changed somehow. You can specify a recommended polling |
1587 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2619 | interval for this case. If you specify a polling interval of C<0> (highly |
1588 | unspecified default> value will be used (which you can expect to be around |
2620 | recommended!) then a I<suitable, unspecified default> value will be used |
1589 | five seconds, although this might change dynamically). Libev will also |
2621 | (which you can expect to be around five seconds, although this might |
1590 | impose a minimum interval which is currently around C<0.1>, but thats |
2622 | change dynamically). Libev will also impose a minimum interval which is |
1591 | usually overkill. |
2623 | currently around C<0.1>, but that's usually overkill. |
1592 | |
2624 | |
1593 | This watcher type is not meant for massive numbers of stat watchers, |
2625 | This watcher type is not meant for massive numbers of stat watchers, |
1594 | as even with OS-supported change notifications, this can be |
2626 | as even with OS-supported change notifications, this can be |
1595 | resource-intensive. |
2627 | resource-intensive. |
1596 | |
2628 | |
1597 | At the time of this writing, only the Linux inotify interface is |
2629 | At the time of this writing, the only OS-specific interface implemented |
1598 | implemented (implementing kqueue support is left as an exercise for the |
2630 | is the Linux inotify interface (implementing kqueue support is left as an |
1599 | reader). Inotify will be used to give hints only and should not change the |
2631 | exercise for the reader. Note, however, that the author sees no way of |
1600 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
2632 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1601 | to fall back to regular polling again even with inotify, but changes are |
|
|
1602 | usually detected immediately, and if the file exists there will be no |
|
|
1603 | polling. |
|
|
1604 | |
2633 | |
1605 | =head3 Inotify |
2634 | =head3 ABI Issues (Largefile Support) |
1606 | |
2635 | |
|
|
2636 | Libev by default (unless the user overrides this) uses the default |
|
|
2637 | compilation environment, which means that on systems with large file |
|
|
2638 | support disabled by default, you get the 32 bit version of the stat |
|
|
2639 | structure. When using the library from programs that change the ABI to |
|
|
2640 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2641 | compile libev with the same flags to get binary compatibility. This is |
|
|
2642 | obviously the case with any flags that change the ABI, but the problem is |
|
|
2643 | most noticeably displayed with ev_stat and large file support. |
|
|
2644 | |
|
|
2645 | The solution for this is to lobby your distribution maker to make large |
|
|
2646 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2647 | optional. Libev cannot simply switch on large file support because it has |
|
|
2648 | to exchange stat structures with application programs compiled using the |
|
|
2649 | default compilation environment. |
|
|
2650 | |
|
|
2651 | =head3 Inotify and Kqueue |
|
|
2652 | |
1607 | When C<inotify (7)> support has been compiled into libev (generally only |
2653 | When C<inotify (7)> support has been compiled into libev and present at |
1608 | available on Linux) and present at runtime, it will be used to speed up |
2654 | runtime, it will be used to speed up change detection where possible. The |
1609 | change detection where possible. The inotify descriptor will be created lazily |
2655 | inotify descriptor will be created lazily when the first C<ev_stat> |
1610 | when the first C<ev_stat> watcher is being started. |
2656 | watcher is being started. |
1611 | |
2657 | |
1612 | Inotify presense does not change the semantics of C<ev_stat> watchers |
2658 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1613 | except that changes might be detected earlier, and in some cases, to avoid |
2659 | except that changes might be detected earlier, and in some cases, to avoid |
1614 | making regular C<stat> calls. Even in the presense of inotify support |
2660 | making regular C<stat> calls. Even in the presence of inotify support |
1615 | there are many cases where libev has to resort to regular C<stat> polling. |
2661 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2662 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2663 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2664 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2665 | xfs are fully working) libev usually gets away without polling. |
1616 | |
2666 | |
1617 | (There is no support for kqueue, as apparently it cannot be used to |
2667 | There is no support for kqueue, as apparently it cannot be used to |
1618 | implement this functionality, due to the requirement of having a file |
2668 | implement this functionality, due to the requirement of having a file |
1619 | descriptor open on the object at all times). |
2669 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2670 | etc. is difficult. |
|
|
2671 | |
|
|
2672 | =head3 C<stat ()> is a synchronous operation |
|
|
2673 | |
|
|
2674 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2675 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2676 | ()>, which is a synchronous operation. |
|
|
2677 | |
|
|
2678 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2679 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2680 | as the path data is usually in memory already (except when starting the |
|
|
2681 | watcher). |
|
|
2682 | |
|
|
2683 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2684 | time due to network issues, and even under good conditions, a stat call |
|
|
2685 | often takes multiple milliseconds. |
|
|
2686 | |
|
|
2687 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2688 | paths, although this is fully supported by libev. |
1620 | |
2689 | |
1621 | =head3 The special problem of stat time resolution |
2690 | =head3 The special problem of stat time resolution |
1622 | |
2691 | |
1623 | The C<stat ()> syscall only supports full-second resolution portably, and |
2692 | The C<stat ()> system call only supports full-second resolution portably, |
1624 | even on systems where the resolution is higher, many filesystems still |
2693 | and even on systems where the resolution is higher, most file systems |
1625 | only support whole seconds. |
2694 | still only support whole seconds. |
1626 | |
2695 | |
1627 | That means that, if the time is the only thing that changes, you might |
2696 | That means that, if the time is the only thing that changes, you can |
1628 | miss updates: on the first update, C<ev_stat> detects a change and calls |
2697 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1629 | your callback, which does something. When there is another update within |
2698 | calls your callback, which does something. When there is another update |
1630 | the same second, C<ev_stat> will be unable to detect it. |
2699 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2700 | stat data does change in other ways (e.g. file size). |
1631 | |
2701 | |
1632 | The solution to this is to delay acting on a change for a second (or till |
2702 | The solution to this is to delay acting on a change for slightly more |
1633 | the next second boundary), using a roughly one-second delay C<ev_timer> |
2703 | than a second (or till slightly after the next full second boundary), using |
1634 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
2704 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1635 | is added to work around small timing inconsistencies of some operating |
2705 | ev_timer_again (loop, w)>). |
1636 | systems. |
2706 | |
|
|
2707 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2708 | of some operating systems (where the second counter of the current time |
|
|
2709 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2710 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2711 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2712 | update file times then there will be a small window where the kernel uses |
|
|
2713 | the previous second to update file times but libev might already execute |
|
|
2714 | the timer callback). |
1637 | |
2715 | |
1638 | =head3 Watcher-Specific Functions and Data Members |
2716 | =head3 Watcher-Specific Functions and Data Members |
1639 | |
2717 | |
1640 | =over 4 |
2718 | =over 4 |
1641 | |
2719 | |
… | |
… | |
1647 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2725 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1648 | be detected and should normally be specified as C<0> to let libev choose |
2726 | be detected and should normally be specified as C<0> to let libev choose |
1649 | a suitable value. The memory pointed to by C<path> must point to the same |
2727 | a suitable value. The memory pointed to by C<path> must point to the same |
1650 | path for as long as the watcher is active. |
2728 | path for as long as the watcher is active. |
1651 | |
2729 | |
1652 | The callback will be receive C<EV_STAT> when a change was detected, |
2730 | The callback will receive an C<EV_STAT> event when a change was detected, |
1653 | relative to the attributes at the time the watcher was started (or the |
2731 | relative to the attributes at the time the watcher was started (or the |
1654 | last change was detected). |
2732 | last change was detected). |
1655 | |
2733 | |
1656 | =item ev_stat_stat (loop, ev_stat *) |
2734 | =item ev_stat_stat (loop, ev_stat *) |
1657 | |
2735 | |
1658 | Updates the stat buffer immediately with new values. If you change the |
2736 | Updates the stat buffer immediately with new values. If you change the |
1659 | watched path in your callback, you could call this fucntion to avoid |
2737 | watched path in your callback, you could call this function to avoid |
1660 | detecting this change (while introducing a race condition). Can also be |
2738 | detecting this change (while introducing a race condition if you are not |
1661 | useful simply to find out the new values. |
2739 | the only one changing the path). Can also be useful simply to find out the |
|
|
2740 | new values. |
1662 | |
2741 | |
1663 | =item ev_statdata attr [read-only] |
2742 | =item ev_statdata attr [read-only] |
1664 | |
2743 | |
1665 | The most-recently detected attributes of the file. Although the type is of |
2744 | The most-recently detected attributes of the file. Although the type is |
1666 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
2745 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1667 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
2746 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2747 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1668 | was some error while C<stat>ing the file. |
2748 | some error while C<stat>ing the file. |
1669 | |
2749 | |
1670 | =item ev_statdata prev [read-only] |
2750 | =item ev_statdata prev [read-only] |
1671 | |
2751 | |
1672 | The previous attributes of the file. The callback gets invoked whenever |
2752 | The previous attributes of the file. The callback gets invoked whenever |
1673 | C<prev> != C<attr>. |
2753 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2754 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2755 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1674 | |
2756 | |
1675 | =item ev_tstamp interval [read-only] |
2757 | =item ev_tstamp interval [read-only] |
1676 | |
2758 | |
1677 | The specified interval. |
2759 | The specified interval. |
1678 | |
2760 | |
1679 | =item const char *path [read-only] |
2761 | =item const char *path [read-only] |
1680 | |
2762 | |
1681 | The filesystem path that is being watched. |
2763 | The file system path that is being watched. |
1682 | |
2764 | |
1683 | =back |
2765 | =back |
1684 | |
2766 | |
1685 | =head3 Examples |
2767 | =head3 Examples |
1686 | |
2768 | |
1687 | Example: Watch C</etc/passwd> for attribute changes. |
2769 | Example: Watch C</etc/passwd> for attribute changes. |
1688 | |
2770 | |
1689 | static void |
2771 | static void |
1690 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2772 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1691 | { |
2773 | { |
1692 | /* /etc/passwd changed in some way */ |
2774 | /* /etc/passwd changed in some way */ |
1693 | if (w->attr.st_nlink) |
2775 | if (w->attr.st_nlink) |
1694 | { |
2776 | { |
1695 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2777 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1696 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2778 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1697 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2779 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1698 | } |
2780 | } |
1699 | else |
2781 | else |
1700 | /* you shalt not abuse printf for puts */ |
2782 | /* you shalt not abuse printf for puts */ |
1701 | puts ("wow, /etc/passwd is not there, expect problems. " |
2783 | puts ("wow, /etc/passwd is not there, expect problems. " |
1702 | "if this is windows, they already arrived\n"); |
2784 | "if this is windows, they already arrived\n"); |
1703 | } |
2785 | } |
1704 | |
2786 | |
1705 | ... |
2787 | ... |
1706 | ev_stat passwd; |
2788 | ev_stat passwd; |
1707 | |
2789 | |
1708 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2790 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1709 | ev_stat_start (loop, &passwd); |
2791 | ev_stat_start (loop, &passwd); |
1710 | |
2792 | |
1711 | Example: Like above, but additionally use a one-second delay so we do not |
2793 | Example: Like above, but additionally use a one-second delay so we do not |
1712 | miss updates (however, frequent updates will delay processing, too, so |
2794 | miss updates (however, frequent updates will delay processing, too, so |
1713 | one might do the work both on C<ev_stat> callback invocation I<and> on |
2795 | one might do the work both on C<ev_stat> callback invocation I<and> on |
1714 | C<ev_timer> callback invocation). |
2796 | C<ev_timer> callback invocation). |
1715 | |
2797 | |
1716 | static ev_stat passwd; |
2798 | static ev_stat passwd; |
1717 | static ev_timer timer; |
2799 | static ev_timer timer; |
1718 | |
2800 | |
1719 | static void |
2801 | static void |
1720 | timer_cb (EV_P_ ev_timer *w, int revents) |
2802 | timer_cb (EV_P_ ev_timer *w, int revents) |
1721 | { |
2803 | { |
1722 | ev_timer_stop (EV_A_ w); |
2804 | ev_timer_stop (EV_A_ w); |
1723 | |
2805 | |
1724 | /* now it's one second after the most recent passwd change */ |
2806 | /* now it's one second after the most recent passwd change */ |
1725 | } |
2807 | } |
1726 | |
2808 | |
1727 | static void |
2809 | static void |
1728 | stat_cb (EV_P_ ev_stat *w, int revents) |
2810 | stat_cb (EV_P_ ev_stat *w, int revents) |
1729 | { |
2811 | { |
1730 | /* reset the one-second timer */ |
2812 | /* reset the one-second timer */ |
1731 | ev_timer_again (EV_A_ &timer); |
2813 | ev_timer_again (EV_A_ &timer); |
1732 | } |
2814 | } |
1733 | |
2815 | |
1734 | ... |
2816 | ... |
1735 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2817 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1736 | ev_stat_start (loop, &passwd); |
2818 | ev_stat_start (loop, &passwd); |
1737 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
2819 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1738 | |
2820 | |
1739 | |
2821 | |
1740 | =head2 C<ev_idle> - when you've got nothing better to do... |
2822 | =head2 C<ev_idle> - when you've got nothing better to do... |
1741 | |
2823 | |
1742 | Idle watchers trigger events when no other events of the same or higher |
2824 | Idle watchers trigger events when no other events of the same or higher |
1743 | priority are pending (prepare, check and other idle watchers do not |
2825 | priority are pending (prepare, check and other idle watchers do not count |
1744 | count). |
2826 | as receiving "events"). |
1745 | |
2827 | |
1746 | That is, as long as your process is busy handling sockets or timeouts |
2828 | That is, as long as your process is busy handling sockets or timeouts |
1747 | (or even signals, imagine) of the same or higher priority it will not be |
2829 | (or even signals, imagine) of the same or higher priority it will not be |
1748 | triggered. But when your process is idle (or only lower-priority watchers |
2830 | triggered. But when your process is idle (or only lower-priority watchers |
1749 | are pending), the idle watchers are being called once per event loop |
2831 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1760 | |
2842 | |
1761 | =head3 Watcher-Specific Functions and Data Members |
2843 | =head3 Watcher-Specific Functions and Data Members |
1762 | |
2844 | |
1763 | =over 4 |
2845 | =over 4 |
1764 | |
2846 | |
1765 | =item ev_idle_init (ev_signal *, callback) |
2847 | =item ev_idle_init (ev_idle *, callback) |
1766 | |
2848 | |
1767 | Initialises and configures the idle watcher - it has no parameters of any |
2849 | Initialises and configures the idle watcher - it has no parameters of any |
1768 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2850 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1769 | believe me. |
2851 | believe me. |
1770 | |
2852 | |
… | |
… | |
1773 | =head3 Examples |
2855 | =head3 Examples |
1774 | |
2856 | |
1775 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2857 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1776 | callback, free it. Also, use no error checking, as usual. |
2858 | callback, free it. Also, use no error checking, as usual. |
1777 | |
2859 | |
1778 | static void |
2860 | static void |
1779 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2861 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1780 | { |
2862 | { |
1781 | free (w); |
2863 | free (w); |
1782 | // now do something you wanted to do when the program has |
2864 | // now do something you wanted to do when the program has |
1783 | // no longer anything immediate to do. |
2865 | // no longer anything immediate to do. |
1784 | } |
2866 | } |
1785 | |
2867 | |
1786 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2868 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1787 | ev_idle_init (idle_watcher, idle_cb); |
2869 | ev_idle_init (idle_watcher, idle_cb); |
1788 | ev_idle_start (loop, idle_cb); |
2870 | ev_idle_start (loop, idle_watcher); |
1789 | |
2871 | |
1790 | |
2872 | |
1791 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2873 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1792 | |
2874 | |
1793 | Prepare and check watchers are usually (but not always) used in tandem: |
2875 | Prepare and check watchers are usually (but not always) used in pairs: |
1794 | prepare watchers get invoked before the process blocks and check watchers |
2876 | prepare watchers get invoked before the process blocks and check watchers |
1795 | afterwards. |
2877 | afterwards. |
1796 | |
2878 | |
1797 | You I<must not> call C<ev_loop> or similar functions that enter |
2879 | You I<must not> call C<ev_run> or similar functions that enter |
1798 | the current event loop from either C<ev_prepare> or C<ev_check> |
2880 | the current event loop from either C<ev_prepare> or C<ev_check> |
1799 | watchers. Other loops than the current one are fine, however. The |
2881 | watchers. Other loops than the current one are fine, however. The |
1800 | rationale behind this is that you do not need to check for recursion in |
2882 | rationale behind this is that you do not need to check for recursion in |
1801 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2883 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1802 | C<ev_check> so if you have one watcher of each kind they will always be |
2884 | C<ev_check> so if you have one watcher of each kind they will always be |
1803 | called in pairs bracketing the blocking call. |
2885 | called in pairs bracketing the blocking call. |
1804 | |
2886 | |
1805 | Their main purpose is to integrate other event mechanisms into libev and |
2887 | Their main purpose is to integrate other event mechanisms into libev and |
1806 | their use is somewhat advanced. This could be used, for example, to track |
2888 | their use is somewhat advanced. They could be used, for example, to track |
1807 | variable changes, implement your own watchers, integrate net-snmp or a |
2889 | variable changes, implement your own watchers, integrate net-snmp or a |
1808 | coroutine library and lots more. They are also occasionally useful if |
2890 | coroutine library and lots more. They are also occasionally useful if |
1809 | you cache some data and want to flush it before blocking (for example, |
2891 | you cache some data and want to flush it before blocking (for example, |
1810 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2892 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1811 | watcher). |
2893 | watcher). |
1812 | |
2894 | |
1813 | This is done by examining in each prepare call which file descriptors need |
2895 | This is done by examining in each prepare call which file descriptors |
1814 | to be watched by the other library, registering C<ev_io> watchers for |
2896 | need to be watched by the other library, registering C<ev_io> watchers |
1815 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2897 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1816 | provide just this functionality). Then, in the check watcher you check for |
2898 | libraries provide exactly this functionality). Then, in the check watcher, |
1817 | any events that occured (by checking the pending status of all watchers |
2899 | you check for any events that occurred (by checking the pending status |
1818 | and stopping them) and call back into the library. The I/O and timer |
2900 | of all watchers and stopping them) and call back into the library. The |
1819 | callbacks will never actually be called (but must be valid nevertheless, |
2901 | I/O and timer callbacks will never actually be called (but must be valid |
1820 | because you never know, you know?). |
2902 | nevertheless, because you never know, you know?). |
1821 | |
2903 | |
1822 | As another example, the Perl Coro module uses these hooks to integrate |
2904 | As another example, the Perl Coro module uses these hooks to integrate |
1823 | coroutines into libev programs, by yielding to other active coroutines |
2905 | coroutines into libev programs, by yielding to other active coroutines |
1824 | during each prepare and only letting the process block if no coroutines |
2906 | during each prepare and only letting the process block if no coroutines |
1825 | are ready to run (it's actually more complicated: it only runs coroutines |
2907 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1828 | loop from blocking if lower-priority coroutines are active, thus mapping |
2910 | loop from blocking if lower-priority coroutines are active, thus mapping |
1829 | low-priority coroutines to idle/background tasks). |
2911 | low-priority coroutines to idle/background tasks). |
1830 | |
2912 | |
1831 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2913 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1832 | priority, to ensure that they are being run before any other watchers |
2914 | priority, to ensure that they are being run before any other watchers |
|
|
2915 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2916 | |
1833 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2917 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1834 | too) should not activate ("feed") events into libev. While libev fully |
2918 | activate ("feed") events into libev. While libev fully supports this, they |
1835 | supports this, they will be called before other C<ev_check> watchers |
2919 | might get executed before other C<ev_check> watchers did their job. As |
1836 | did their job. As C<ev_check> watchers are often used to embed other |
2920 | C<ev_check> watchers are often used to embed other (non-libev) event |
1837 | (non-libev) event loops those other event loops might be in an unusable |
2921 | loops those other event loops might be in an unusable state until their |
1838 | state until their C<ev_check> watcher ran (always remind yourself to |
2922 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1839 | coexist peacefully with others). |
2923 | others). |
1840 | |
2924 | |
1841 | =head3 Watcher-Specific Functions and Data Members |
2925 | =head3 Watcher-Specific Functions and Data Members |
1842 | |
2926 | |
1843 | =over 4 |
2927 | =over 4 |
1844 | |
2928 | |
… | |
… | |
1846 | |
2930 | |
1847 | =item ev_check_init (ev_check *, callback) |
2931 | =item ev_check_init (ev_check *, callback) |
1848 | |
2932 | |
1849 | Initialises and configures the prepare or check watcher - they have no |
2933 | Initialises and configures the prepare or check watcher - they have no |
1850 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2934 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1851 | macros, but using them is utterly, utterly and completely pointless. |
2935 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2936 | pointless. |
1852 | |
2937 | |
1853 | =back |
2938 | =back |
1854 | |
2939 | |
1855 | =head3 Examples |
2940 | =head3 Examples |
1856 | |
2941 | |
1857 | There are a number of principal ways to embed other event loops or modules |
2942 | There are a number of principal ways to embed other event loops or modules |
1858 | into libev. Here are some ideas on how to include libadns into libev |
2943 | into libev. Here are some ideas on how to include libadns into libev |
1859 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
2944 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1860 | use for an actually working example. Another Perl module named C<EV::Glib> |
2945 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1861 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
2946 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1862 | into the Glib event loop). |
2947 | Glib event loop). |
1863 | |
2948 | |
1864 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
2949 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1865 | and in a check watcher, destroy them and call into libadns. What follows |
2950 | and in a check watcher, destroy them and call into libadns. What follows |
1866 | is pseudo-code only of course. This requires you to either use a low |
2951 | is pseudo-code only of course. This requires you to either use a low |
1867 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
2952 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1868 | the callbacks for the IO/timeout watchers might not have been called yet. |
2953 | the callbacks for the IO/timeout watchers might not have been called yet. |
1869 | |
2954 | |
1870 | static ev_io iow [nfd]; |
2955 | static ev_io iow [nfd]; |
1871 | static ev_timer tw; |
2956 | static ev_timer tw; |
1872 | |
2957 | |
1873 | static void |
2958 | static void |
1874 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2959 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1875 | { |
2960 | { |
1876 | } |
2961 | } |
1877 | |
2962 | |
1878 | // create io watchers for each fd and a timer before blocking |
2963 | // create io watchers for each fd and a timer before blocking |
1879 | static void |
2964 | static void |
1880 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2965 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1881 | { |
2966 | { |
1882 | int timeout = 3600000; |
2967 | int timeout = 3600000; |
1883 | struct pollfd fds [nfd]; |
2968 | struct pollfd fds [nfd]; |
1884 | // actual code will need to loop here and realloc etc. |
2969 | // actual code will need to loop here and realloc etc. |
1885 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2970 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1886 | |
2971 | |
1887 | /* the callback is illegal, but won't be called as we stop during check */ |
2972 | /* the callback is illegal, but won't be called as we stop during check */ |
1888 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2973 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1889 | ev_timer_start (loop, &tw); |
2974 | ev_timer_start (loop, &tw); |
1890 | |
2975 | |
1891 | // create one ev_io per pollfd |
2976 | // create one ev_io per pollfd |
1892 | for (int i = 0; i < nfd; ++i) |
2977 | for (int i = 0; i < nfd; ++i) |
1893 | { |
2978 | { |
1894 | ev_io_init (iow + i, io_cb, fds [i].fd, |
2979 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1895 | ((fds [i].events & POLLIN ? EV_READ : 0) |
2980 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1896 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2981 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1897 | |
2982 | |
1898 | fds [i].revents = 0; |
2983 | fds [i].revents = 0; |
1899 | ev_io_start (loop, iow + i); |
2984 | ev_io_start (loop, iow + i); |
1900 | } |
2985 | } |
1901 | } |
2986 | } |
1902 | |
2987 | |
1903 | // stop all watchers after blocking |
2988 | // stop all watchers after blocking |
1904 | static void |
2989 | static void |
1905 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2990 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1906 | { |
2991 | { |
1907 | ev_timer_stop (loop, &tw); |
2992 | ev_timer_stop (loop, &tw); |
1908 | |
2993 | |
1909 | for (int i = 0; i < nfd; ++i) |
2994 | for (int i = 0; i < nfd; ++i) |
1910 | { |
2995 | { |
1911 | // set the relevant poll flags |
2996 | // set the relevant poll flags |
1912 | // could also call adns_processreadable etc. here |
2997 | // could also call adns_processreadable etc. here |
1913 | struct pollfd *fd = fds + i; |
2998 | struct pollfd *fd = fds + i; |
1914 | int revents = ev_clear_pending (iow + i); |
2999 | int revents = ev_clear_pending (iow + i); |
1915 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
3000 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1916 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
3001 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1917 | |
3002 | |
1918 | // now stop the watcher |
3003 | // now stop the watcher |
1919 | ev_io_stop (loop, iow + i); |
3004 | ev_io_stop (loop, iow + i); |
1920 | } |
3005 | } |
1921 | |
3006 | |
1922 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
3007 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1923 | } |
3008 | } |
1924 | |
3009 | |
1925 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
3010 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
1926 | in the prepare watcher and would dispose of the check watcher. |
3011 | in the prepare watcher and would dispose of the check watcher. |
1927 | |
3012 | |
1928 | Method 3: If the module to be embedded supports explicit event |
3013 | Method 3: If the module to be embedded supports explicit event |
1929 | notification (adns does), you can also make use of the actual watcher |
3014 | notification (libadns does), you can also make use of the actual watcher |
1930 | callbacks, and only destroy/create the watchers in the prepare watcher. |
3015 | callbacks, and only destroy/create the watchers in the prepare watcher. |
1931 | |
3016 | |
1932 | static void |
3017 | static void |
1933 | timer_cb (EV_P_ ev_timer *w, int revents) |
3018 | timer_cb (EV_P_ ev_timer *w, int revents) |
1934 | { |
3019 | { |
1935 | adns_state ads = (adns_state)w->data; |
3020 | adns_state ads = (adns_state)w->data; |
1936 | update_now (EV_A); |
3021 | update_now (EV_A); |
1937 | |
3022 | |
1938 | adns_processtimeouts (ads, &tv_now); |
3023 | adns_processtimeouts (ads, &tv_now); |
1939 | } |
3024 | } |
1940 | |
3025 | |
1941 | static void |
3026 | static void |
1942 | io_cb (EV_P_ ev_io *w, int revents) |
3027 | io_cb (EV_P_ ev_io *w, int revents) |
1943 | { |
3028 | { |
1944 | adns_state ads = (adns_state)w->data; |
3029 | adns_state ads = (adns_state)w->data; |
1945 | update_now (EV_A); |
3030 | update_now (EV_A); |
1946 | |
3031 | |
1947 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
3032 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
1948 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
3033 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
1949 | } |
3034 | } |
1950 | |
3035 | |
1951 | // do not ever call adns_afterpoll |
3036 | // do not ever call adns_afterpoll |
1952 | |
3037 | |
1953 | Method 4: Do not use a prepare or check watcher because the module you |
3038 | Method 4: Do not use a prepare or check watcher because the module you |
1954 | want to embed is too inflexible to support it. Instead, youc na override |
3039 | want to embed is not flexible enough to support it. Instead, you can |
1955 | their poll function. The drawback with this solution is that the main |
3040 | override their poll function. The drawback with this solution is that the |
1956 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
3041 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
1957 | this. |
3042 | this approach, effectively embedding EV as a client into the horrible |
|
|
3043 | libglib event loop. |
1958 | |
3044 | |
1959 | static gint |
3045 | static gint |
1960 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
3046 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
1961 | { |
3047 | { |
1962 | int got_events = 0; |
3048 | int got_events = 0; |
1963 | |
3049 | |
1964 | for (n = 0; n < nfds; ++n) |
3050 | for (n = 0; n < nfds; ++n) |
1965 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
3051 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
1966 | |
3052 | |
1967 | if (timeout >= 0) |
3053 | if (timeout >= 0) |
1968 | // create/start timer |
3054 | // create/start timer |
1969 | |
3055 | |
1970 | // poll |
3056 | // poll |
1971 | ev_loop (EV_A_ 0); |
3057 | ev_run (EV_A_ 0); |
1972 | |
3058 | |
1973 | // stop timer again |
3059 | // stop timer again |
1974 | if (timeout >= 0) |
3060 | if (timeout >= 0) |
1975 | ev_timer_stop (EV_A_ &to); |
3061 | ev_timer_stop (EV_A_ &to); |
1976 | |
3062 | |
1977 | // stop io watchers again - their callbacks should have set |
3063 | // stop io watchers again - their callbacks should have set |
1978 | for (n = 0; n < nfds; ++n) |
3064 | for (n = 0; n < nfds; ++n) |
1979 | ev_io_stop (EV_A_ iow [n]); |
3065 | ev_io_stop (EV_A_ iow [n]); |
1980 | |
3066 | |
1981 | return got_events; |
3067 | return got_events; |
1982 | } |
3068 | } |
1983 | |
3069 | |
1984 | |
3070 | |
1985 | =head2 C<ev_embed> - when one backend isn't enough... |
3071 | =head2 C<ev_embed> - when one backend isn't enough... |
1986 | |
3072 | |
1987 | This is a rather advanced watcher type that lets you embed one event loop |
3073 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
1993 | prioritise I/O. |
3079 | prioritise I/O. |
1994 | |
3080 | |
1995 | As an example for a bug workaround, the kqueue backend might only support |
3081 | As an example for a bug workaround, the kqueue backend might only support |
1996 | sockets on some platform, so it is unusable as generic backend, but you |
3082 | sockets on some platform, so it is unusable as generic backend, but you |
1997 | still want to make use of it because you have many sockets and it scales |
3083 | still want to make use of it because you have many sockets and it scales |
1998 | so nicely. In this case, you would create a kqueue-based loop and embed it |
3084 | so nicely. In this case, you would create a kqueue-based loop and embed |
1999 | into your default loop (which might use e.g. poll). Overall operation will |
3085 | it into your default loop (which might use e.g. poll). Overall operation |
2000 | be a bit slower because first libev has to poll and then call kevent, but |
3086 | will be a bit slower because first libev has to call C<poll> and then |
2001 | at least you can use both at what they are best. |
3087 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
3088 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2002 | |
3089 | |
2003 | As for prioritising I/O: rarely you have the case where some fds have |
3090 | As for prioritising I/O: under rare circumstances you have the case where |
2004 | to be watched and handled very quickly (with low latency), and even |
3091 | some fds have to be watched and handled very quickly (with low latency), |
2005 | priorities and idle watchers might have too much overhead. In this case |
3092 | and even priorities and idle watchers might have too much overhead. In |
2006 | you would put all the high priority stuff in one loop and all the rest in |
3093 | this case you would put all the high priority stuff in one loop and all |
2007 | a second one, and embed the second one in the first. |
3094 | the rest in a second one, and embed the second one in the first. |
2008 | |
3095 | |
2009 | As long as the watcher is active, the callback will be invoked every time |
3096 | As long as the watcher is active, the callback will be invoked every |
2010 | there might be events pending in the embedded loop. The callback must then |
3097 | time there might be events pending in the embedded loop. The callback |
2011 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
3098 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2012 | their callbacks (you could also start an idle watcher to give the embedded |
3099 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2013 | loop strictly lower priority for example). You can also set the callback |
3100 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2014 | to C<0>, in which case the embed watcher will automatically execute the |
3101 | to give the embedded loop strictly lower priority for example). |
2015 | embedded loop sweep. |
|
|
2016 | |
3102 | |
2017 | As long as the watcher is started it will automatically handle events. The |
3103 | You can also set the callback to C<0>, in which case the embed watcher |
2018 | callback will be invoked whenever some events have been handled. You can |
3104 | will automatically execute the embedded loop sweep whenever necessary. |
2019 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2020 | interested in that. |
|
|
2021 | |
3105 | |
2022 | Also, there have not currently been made special provisions for forking: |
3106 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2023 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
3107 | is active, i.e., the embedded loop will automatically be forked when the |
2024 | but you will also have to stop and restart any C<ev_embed> watchers |
3108 | embedding loop forks. In other cases, the user is responsible for calling |
2025 | yourself. |
3109 | C<ev_loop_fork> on the embedded loop. |
2026 | |
3110 | |
2027 | Unfortunately, not all backends are embeddable, only the ones returned by |
3111 | Unfortunately, not all backends are embeddable: only the ones returned by |
2028 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
3112 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2029 | portable one. |
3113 | portable one. |
2030 | |
3114 | |
2031 | So when you want to use this feature you will always have to be prepared |
3115 | So when you want to use this feature you will always have to be prepared |
2032 | that you cannot get an embeddable loop. The recommended way to get around |
3116 | that you cannot get an embeddable loop. The recommended way to get around |
2033 | this is to have a separate variables for your embeddable loop, try to |
3117 | this is to have a separate variables for your embeddable loop, try to |
2034 | create it, and if that fails, use the normal loop for everything. |
3118 | create it, and if that fails, use the normal loop for everything. |
2035 | |
3119 | |
|
|
3120 | =head3 C<ev_embed> and fork |
|
|
3121 | |
|
|
3122 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
3123 | automatically be applied to the embedded loop as well, so no special |
|
|
3124 | fork handling is required in that case. When the watcher is not running, |
|
|
3125 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
3126 | as applicable. |
|
|
3127 | |
2036 | =head3 Watcher-Specific Functions and Data Members |
3128 | =head3 Watcher-Specific Functions and Data Members |
2037 | |
3129 | |
2038 | =over 4 |
3130 | =over 4 |
2039 | |
3131 | |
2040 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3132 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
2043 | |
3135 | |
2044 | Configures the watcher to embed the given loop, which must be |
3136 | Configures the watcher to embed the given loop, which must be |
2045 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3137 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2046 | invoked automatically, otherwise it is the responsibility of the callback |
3138 | invoked automatically, otherwise it is the responsibility of the callback |
2047 | to invoke it (it will continue to be called until the sweep has been done, |
3139 | to invoke it (it will continue to be called until the sweep has been done, |
2048 | if you do not want thta, you need to temporarily stop the embed watcher). |
3140 | if you do not want that, you need to temporarily stop the embed watcher). |
2049 | |
3141 | |
2050 | =item ev_embed_sweep (loop, ev_embed *) |
3142 | =item ev_embed_sweep (loop, ev_embed *) |
2051 | |
3143 | |
2052 | Make a single, non-blocking sweep over the embedded loop. This works |
3144 | Make a single, non-blocking sweep over the embedded loop. This works |
2053 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3145 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2054 | apropriate way for embedded loops. |
3146 | appropriate way for embedded loops. |
2055 | |
3147 | |
2056 | =item struct ev_loop *other [read-only] |
3148 | =item struct ev_loop *other [read-only] |
2057 | |
3149 | |
2058 | The embedded event loop. |
3150 | The embedded event loop. |
2059 | |
3151 | |
… | |
… | |
2061 | |
3153 | |
2062 | =head3 Examples |
3154 | =head3 Examples |
2063 | |
3155 | |
2064 | Example: Try to get an embeddable event loop and embed it into the default |
3156 | Example: Try to get an embeddable event loop and embed it into the default |
2065 | event loop. If that is not possible, use the default loop. The default |
3157 | event loop. If that is not possible, use the default loop. The default |
2066 | loop is stored in C<loop_hi>, while the mebeddable loop is stored in |
3158 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
2067 | C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be |
3159 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2068 | used). |
3160 | used). |
2069 | |
3161 | |
2070 | struct ev_loop *loop_hi = ev_default_init (0); |
3162 | struct ev_loop *loop_hi = ev_default_init (0); |
2071 | struct ev_loop *loop_lo = 0; |
3163 | struct ev_loop *loop_lo = 0; |
2072 | struct ev_embed embed; |
3164 | ev_embed embed; |
2073 | |
3165 | |
2074 | // see if there is a chance of getting one that works |
3166 | // see if there is a chance of getting one that works |
2075 | // (remember that a flags value of 0 means autodetection) |
3167 | // (remember that a flags value of 0 means autodetection) |
2076 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3168 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2077 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3169 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2078 | : 0; |
3170 | : 0; |
2079 | |
3171 | |
2080 | // if we got one, then embed it, otherwise default to loop_hi |
3172 | // if we got one, then embed it, otherwise default to loop_hi |
2081 | if (loop_lo) |
3173 | if (loop_lo) |
2082 | { |
3174 | { |
2083 | ev_embed_init (&embed, 0, loop_lo); |
3175 | ev_embed_init (&embed, 0, loop_lo); |
2084 | ev_embed_start (loop_hi, &embed); |
3176 | ev_embed_start (loop_hi, &embed); |
2085 | } |
3177 | } |
2086 | else |
3178 | else |
2087 | loop_lo = loop_hi; |
3179 | loop_lo = loop_hi; |
2088 | |
3180 | |
2089 | Example: Check if kqueue is available but not recommended and create |
3181 | Example: Check if kqueue is available but not recommended and create |
2090 | a kqueue backend for use with sockets (which usually work with any |
3182 | a kqueue backend for use with sockets (which usually work with any |
2091 | kqueue implementation). Store the kqueue/socket-only event loop in |
3183 | kqueue implementation). Store the kqueue/socket-only event loop in |
2092 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3184 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2093 | |
3185 | |
2094 | struct ev_loop *loop = ev_default_init (0); |
3186 | struct ev_loop *loop = ev_default_init (0); |
2095 | struct ev_loop *loop_socket = 0; |
3187 | struct ev_loop *loop_socket = 0; |
2096 | struct ev_embed embed; |
3188 | ev_embed embed; |
2097 | |
3189 | |
2098 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3190 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2099 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3191 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2100 | { |
3192 | { |
2101 | ev_embed_init (&embed, 0, loop_socket); |
3193 | ev_embed_init (&embed, 0, loop_socket); |
2102 | ev_embed_start (loop, &embed); |
3194 | ev_embed_start (loop, &embed); |
2103 | } |
3195 | } |
2104 | |
3196 | |
2105 | if (!loop_socket) |
3197 | if (!loop_socket) |
2106 | loop_socket = loop; |
3198 | loop_socket = loop; |
2107 | |
3199 | |
2108 | // now use loop_socket for all sockets, and loop for everything else |
3200 | // now use loop_socket for all sockets, and loop for everything else |
2109 | |
3201 | |
2110 | |
3202 | |
2111 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3203 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2112 | |
3204 | |
2113 | Fork watchers are called when a C<fork ()> was detected (usually because |
3205 | Fork watchers are called when a C<fork ()> was detected (usually because |
… | |
… | |
2116 | event loop blocks next and before C<ev_check> watchers are being called, |
3208 | event loop blocks next and before C<ev_check> watchers are being called, |
2117 | and only in the child after the fork. If whoever good citizen calling |
3209 | and only in the child after the fork. If whoever good citizen calling |
2118 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3210 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2119 | handlers will be invoked, too, of course. |
3211 | handlers will be invoked, too, of course. |
2120 | |
3212 | |
|
|
3213 | =head3 The special problem of life after fork - how is it possible? |
|
|
3214 | |
|
|
3215 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3216 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3217 | sequence should be handled by libev without any problems. |
|
|
3218 | |
|
|
3219 | This changes when the application actually wants to do event handling |
|
|
3220 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3221 | fork. |
|
|
3222 | |
|
|
3223 | The default mode of operation (for libev, with application help to detect |
|
|
3224 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3225 | when I<either> the parent I<or> the child process continues. |
|
|
3226 | |
|
|
3227 | When both processes want to continue using libev, then this is usually the |
|
|
3228 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3229 | supposed to continue with all watchers in place as before, while the other |
|
|
3230 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3231 | |
|
|
3232 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3233 | simply create a new event loop, which of course will be "empty", and |
|
|
3234 | use that for new watchers. This has the advantage of not touching more |
|
|
3235 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3236 | disadvantage of having to use multiple event loops (which do not support |
|
|
3237 | signal watchers). |
|
|
3238 | |
|
|
3239 | When this is not possible, or you want to use the default loop for |
|
|
3240 | other reasons, then in the process that wants to start "fresh", call |
|
|
3241 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3242 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3243 | watchers, so you have to be careful not to execute code that modifies |
|
|
3244 | those watchers. Note also that in that case, you have to re-register any |
|
|
3245 | signal watchers. |
|
|
3246 | |
2121 | =head3 Watcher-Specific Functions and Data Members |
3247 | =head3 Watcher-Specific Functions and Data Members |
2122 | |
3248 | |
2123 | =over 4 |
3249 | =over 4 |
2124 | |
3250 | |
2125 | =item ev_fork_init (ev_signal *, callback) |
3251 | =item ev_fork_init (ev_fork *, callback) |
2126 | |
3252 | |
2127 | Initialises and configures the fork watcher - it has no parameters of any |
3253 | Initialises and configures the fork watcher - it has no parameters of any |
2128 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3254 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2129 | believe me. |
3255 | really. |
2130 | |
3256 | |
2131 | =back |
3257 | =back |
2132 | |
3258 | |
2133 | |
3259 | |
|
|
3260 | =head2 C<ev_cleanup> - even the best things end |
|
|
3261 | |
|
|
3262 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3263 | by a call to C<ev_loop_destroy>. |
|
|
3264 | |
|
|
3265 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3266 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3267 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3268 | loop when you want them to be invoked. |
|
|
3269 | |
|
|
3270 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3271 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3272 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3273 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3274 | |
|
|
3275 | =head3 Watcher-Specific Functions and Data Members |
|
|
3276 | |
|
|
3277 | =over 4 |
|
|
3278 | |
|
|
3279 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3280 | |
|
|
3281 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3282 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3283 | pointless, I assure you. |
|
|
3284 | |
|
|
3285 | =back |
|
|
3286 | |
|
|
3287 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3288 | cleanup functions are called. |
|
|
3289 | |
|
|
3290 | static void |
|
|
3291 | program_exits (void) |
|
|
3292 | { |
|
|
3293 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3294 | } |
|
|
3295 | |
|
|
3296 | ... |
|
|
3297 | atexit (program_exits); |
|
|
3298 | |
|
|
3299 | |
2134 | =head2 C<ev_async> - how to wake up another event loop |
3300 | =head2 C<ev_async> - how to wake up an event loop |
2135 | |
3301 | |
2136 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3302 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2137 | asynchronous sources such as signal handlers (as opposed to multiple event |
3303 | asynchronous sources such as signal handlers (as opposed to multiple event |
2138 | loops - those are of course safe to use in different threads). |
3304 | loops - those are of course safe to use in different threads). |
2139 | |
3305 | |
2140 | Sometimes, however, you need to wake up another event loop you do not |
3306 | Sometimes, however, you need to wake up an event loop you do not control, |
2141 | control, for example because it belongs to another thread. This is what |
3307 | for example because it belongs to another thread. This is what C<ev_async> |
2142 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3308 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2143 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3309 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2144 | safe. |
|
|
2145 | |
3310 | |
2146 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3311 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2147 | too, are asynchronous in nature, and signals, too, will be compressed |
3312 | too, are asynchronous in nature, and signals, too, will be compressed |
2148 | (i.e. the number of callback invocations may be less than the number of |
3313 | (i.e. the number of callback invocations may be less than the number of |
2149 | C<ev_async_sent> calls). |
3314 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
2150 | |
3315 | of "global async watchers" by using a watcher on an otherwise unused |
2151 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3316 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2152 | just the default loop. |
3317 | even without knowing which loop owns the signal. |
2153 | |
3318 | |
2154 | =head3 Queueing |
3319 | =head3 Queueing |
2155 | |
3320 | |
2156 | C<ev_async> does not support queueing of data in any way. The reason |
3321 | C<ev_async> does not support queueing of data in any way. The reason |
2157 | is that the author does not know of a simple (or any) algorithm for a |
3322 | is that the author does not know of a simple (or any) algorithm for a |
2158 | multiple-writer-single-reader queue that works in all cases and doesn't |
3323 | multiple-writer-single-reader queue that works in all cases and doesn't |
2159 | need elaborate support such as pthreads. |
3324 | need elaborate support such as pthreads or unportable memory access |
|
|
3325 | semantics. |
2160 | |
3326 | |
2161 | That means that if you want to queue data, you have to provide your own |
3327 | That means that if you want to queue data, you have to provide your own |
2162 | queue. But at least I can tell you would implement locking around your |
3328 | queue. But at least I can tell you how to implement locking around your |
2163 | queue: |
3329 | queue: |
2164 | |
3330 | |
2165 | =over 4 |
3331 | =over 4 |
2166 | |
3332 | |
2167 | =item queueing from a signal handler context |
3333 | =item queueing from a signal handler context |
2168 | |
3334 | |
2169 | To implement race-free queueing, you simply add to the queue in the signal |
3335 | To implement race-free queueing, you simply add to the queue in the signal |
2170 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3336 | handler but you block the signal handler in the watcher callback. Here is |
2171 | some fictitiuous SIGUSR1 handler: |
3337 | an example that does that for some fictitious SIGUSR1 handler: |
2172 | |
3338 | |
2173 | static ev_async mysig; |
3339 | static ev_async mysig; |
2174 | |
3340 | |
2175 | static void |
3341 | static void |
2176 | sigusr1_handler (void) |
3342 | sigusr1_handler (void) |
… | |
… | |
2242 | =over 4 |
3408 | =over 4 |
2243 | |
3409 | |
2244 | =item ev_async_init (ev_async *, callback) |
3410 | =item ev_async_init (ev_async *, callback) |
2245 | |
3411 | |
2246 | Initialises and configures the async watcher - it has no parameters of any |
3412 | Initialises and configures the async watcher - it has no parameters of any |
2247 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3413 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2248 | believe me. |
3414 | trust me. |
2249 | |
3415 | |
2250 | =item ev_async_send (loop, ev_async *) |
3416 | =item ev_async_send (loop, ev_async *) |
2251 | |
3417 | |
2252 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3418 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2253 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3419 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3420 | returns. |
|
|
3421 | |
2254 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3422 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2255 | similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding |
3423 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2256 | section below on what exactly this means). |
3424 | embedding section below on what exactly this means). |
2257 | |
3425 | |
2258 | This call incurs the overhead of a syscall only once per loop iteration, |
3426 | Note that, as with other watchers in libev, multiple events might get |
2259 | so while the overhead might be noticable, it doesn't apply to repeated |
3427 | compressed into a single callback invocation (another way to look at |
2260 | calls to C<ev_async_send>. |
3428 | this is that C<ev_async> watchers are level-triggered: they are set on |
|
|
3429 | C<ev_async_send>, reset when the event loop detects that). |
|
|
3430 | |
|
|
3431 | This call incurs the overhead of at most one extra system call per event |
|
|
3432 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3433 | the event loop (or your program) is processing events. That means that |
|
|
3434 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3435 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3436 | zero) under load. |
|
|
3437 | |
|
|
3438 | =item bool = ev_async_pending (ev_async *) |
|
|
3439 | |
|
|
3440 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
3441 | watcher but the event has not yet been processed (or even noted) by the |
|
|
3442 | event loop. |
|
|
3443 | |
|
|
3444 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
3445 | the loop iterates next and checks for the watcher to have become active, |
|
|
3446 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
3447 | quickly check whether invoking the loop might be a good idea. |
|
|
3448 | |
|
|
3449 | Not that this does I<not> check whether the watcher itself is pending, |
|
|
3450 | only whether it has been requested to make this watcher pending: there |
|
|
3451 | is a time window between the event loop checking and resetting the async |
|
|
3452 | notification, and the callback being invoked. |
2261 | |
3453 | |
2262 | =back |
3454 | =back |
2263 | |
3455 | |
2264 | |
3456 | |
2265 | =head1 OTHER FUNCTIONS |
3457 | =head1 OTHER FUNCTIONS |
… | |
… | |
2269 | =over 4 |
3461 | =over 4 |
2270 | |
3462 | |
2271 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3463 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2272 | |
3464 | |
2273 | This function combines a simple timer and an I/O watcher, calls your |
3465 | This function combines a simple timer and an I/O watcher, calls your |
2274 | callback on whichever event happens first and automatically stop both |
3466 | callback on whichever event happens first and automatically stops both |
2275 | watchers. This is useful if you want to wait for a single event on an fd |
3467 | watchers. This is useful if you want to wait for a single event on an fd |
2276 | or timeout without having to allocate/configure/start/stop/free one or |
3468 | or timeout without having to allocate/configure/start/stop/free one or |
2277 | more watchers yourself. |
3469 | more watchers yourself. |
2278 | |
3470 | |
2279 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3471 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2280 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3472 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2281 | C<events> set will be craeted and started. |
3473 | the given C<fd> and C<events> set will be created and started. |
2282 | |
3474 | |
2283 | If C<timeout> is less than 0, then no timeout watcher will be |
3475 | If C<timeout> is less than 0, then no timeout watcher will be |
2284 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3476 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2285 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3477 | repeat = 0) will be started. C<0> is a valid timeout. |
2286 | dubious value. |
|
|
2287 | |
3478 | |
2288 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3479 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2289 | passed an C<revents> set like normal event callbacks (a combination of |
3480 | passed an C<revents> set like normal event callbacks (a combination of |
2290 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3481 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2291 | value passed to C<ev_once>: |
3482 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3483 | a timeout and an io event at the same time - you probably should give io |
|
|
3484 | events precedence. |
2292 | |
3485 | |
|
|
3486 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
3487 | |
2293 | static void stdin_ready (int revents, void *arg) |
3488 | static void stdin_ready (int revents, void *arg) |
|
|
3489 | { |
|
|
3490 | if (revents & EV_READ) |
|
|
3491 | /* stdin might have data for us, joy! */; |
|
|
3492 | else if (revents & EV_TIMER) |
|
|
3493 | /* doh, nothing entered */; |
|
|
3494 | } |
|
|
3495 | |
|
|
3496 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
|
|
3497 | |
|
|
3498 | =item ev_feed_fd_event (loop, int fd, int revents) |
|
|
3499 | |
|
|
3500 | Feed an event on the given fd, as if a file descriptor backend detected |
|
|
3501 | the given events. |
|
|
3502 | |
|
|
3503 | =item ev_feed_signal_event (loop, int signum) |
|
|
3504 | |
|
|
3505 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
|
|
3506 | which is async-safe. |
|
|
3507 | |
|
|
3508 | =back |
|
|
3509 | |
|
|
3510 | |
|
|
3511 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3512 | |
|
|
3513 | This section explains some common idioms that are not immediately |
|
|
3514 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3515 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3516 | |
|
|
3517 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3518 | |
|
|
3519 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3520 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3521 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3522 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3523 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3524 | data: |
|
|
3525 | |
|
|
3526 | struct my_io |
|
|
3527 | { |
|
|
3528 | ev_io io; |
|
|
3529 | int otherfd; |
|
|
3530 | void *somedata; |
|
|
3531 | struct whatever *mostinteresting; |
|
|
3532 | }; |
|
|
3533 | |
|
|
3534 | ... |
|
|
3535 | struct my_io w; |
|
|
3536 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3537 | |
|
|
3538 | And since your callback will be called with a pointer to the watcher, you |
|
|
3539 | can cast it back to your own type: |
|
|
3540 | |
|
|
3541 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3542 | { |
|
|
3543 | struct my_io *w = (struct my_io *)w_; |
|
|
3544 | ... |
|
|
3545 | } |
|
|
3546 | |
|
|
3547 | More interesting and less C-conformant ways of casting your callback |
|
|
3548 | function type instead have been omitted. |
|
|
3549 | |
|
|
3550 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3551 | |
|
|
3552 | Another common scenario is to use some data structure with multiple |
|
|
3553 | embedded watchers, in effect creating your own watcher that combines |
|
|
3554 | multiple libev event sources into one "super-watcher": |
|
|
3555 | |
|
|
3556 | struct my_biggy |
|
|
3557 | { |
|
|
3558 | int some_data; |
|
|
3559 | ev_timer t1; |
|
|
3560 | ev_timer t2; |
|
|
3561 | } |
|
|
3562 | |
|
|
3563 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3564 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3565 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3566 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3567 | real programmers): |
|
|
3568 | |
|
|
3569 | #include <stddef.h> |
|
|
3570 | |
|
|
3571 | static void |
|
|
3572 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3573 | { |
|
|
3574 | struct my_biggy big = (struct my_biggy *) |
|
|
3575 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3576 | } |
|
|
3577 | |
|
|
3578 | static void |
|
|
3579 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3580 | { |
|
|
3581 | struct my_biggy big = (struct my_biggy *) |
|
|
3582 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3583 | } |
|
|
3584 | |
|
|
3585 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3586 | |
|
|
3587 | Often you have structures like this in event-based programs: |
|
|
3588 | |
|
|
3589 | callback () |
2294 | { |
3590 | { |
2295 | if (revents & EV_TIMEOUT) |
3591 | free (request); |
2296 | /* doh, nothing entered */; |
|
|
2297 | else if (revents & EV_READ) |
|
|
2298 | /* stdin might have data for us, joy! */; |
|
|
2299 | } |
3592 | } |
2300 | |
3593 | |
2301 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3594 | request = start_new_request (..., callback); |
2302 | |
3595 | |
2303 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
3596 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3597 | used to cancel the operation, or do other things with it. |
2304 | |
3598 | |
2305 | Feeds the given event set into the event loop, as if the specified event |
3599 | It's not uncommon to have code paths in C<start_new_request> that |
2306 | had happened for the specified watcher (which must be a pointer to an |
3600 | immediately invoke the callback, for example, to report errors. Or you add |
2307 | initialised but not necessarily started event watcher). |
3601 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3602 | operation and simply invoke the callback with the result. |
2308 | |
3603 | |
2309 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3604 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3605 | has returned, so C<request> is not set. |
2310 | |
3606 | |
2311 | Feed an event on the given fd, as if a file descriptor backend detected |
3607 | Even if you pass the request by some safer means to the callback, you |
2312 | the given events it. |
3608 | might want to do something to the request after starting it, such as |
|
|
3609 | canceling it, which probably isn't working so well when the callback has |
|
|
3610 | already been invoked. |
2313 | |
3611 | |
2314 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3612 | A common way around all these issues is to make sure that |
|
|
3613 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3614 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3615 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3616 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3617 | and pushing it into the pending queue: |
2315 | |
3618 | |
2316 | Feed an event as if the given signal occured (C<loop> must be the default |
3619 | ev_set_cb (watcher, callback); |
2317 | loop!). |
3620 | ev_feed_event (EV_A_ watcher, 0); |
2318 | |
3621 | |
2319 | =back |
3622 | This way, C<start_new_request> can safely return before the callback is |
|
|
3623 | invoked, while not delaying callback invocation too much. |
|
|
3624 | |
|
|
3625 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3626 | |
|
|
3627 | Often (especially in GUI toolkits) there are places where you have |
|
|
3628 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3629 | invoking C<ev_run>. |
|
|
3630 | |
|
|
3631 | This brings the problem of exiting - a callback might want to finish the |
|
|
3632 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3633 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3634 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3635 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3636 | |
|
|
3637 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3638 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3639 | triggered, using C<EVRUN_ONCE>: |
|
|
3640 | |
|
|
3641 | // main loop |
|
|
3642 | int exit_main_loop = 0; |
|
|
3643 | |
|
|
3644 | while (!exit_main_loop) |
|
|
3645 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3646 | |
|
|
3647 | // in a modal watcher |
|
|
3648 | int exit_nested_loop = 0; |
|
|
3649 | |
|
|
3650 | while (!exit_nested_loop) |
|
|
3651 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3652 | |
|
|
3653 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3654 | |
|
|
3655 | // exit modal loop |
|
|
3656 | exit_nested_loop = 1; |
|
|
3657 | |
|
|
3658 | // exit main program, after modal loop is finished |
|
|
3659 | exit_main_loop = 1; |
|
|
3660 | |
|
|
3661 | // exit both |
|
|
3662 | exit_main_loop = exit_nested_loop = 1; |
|
|
3663 | |
|
|
3664 | =head2 THREAD LOCKING EXAMPLE |
|
|
3665 | |
|
|
3666 | Here is a fictitious example of how to run an event loop in a different |
|
|
3667 | thread from where callbacks are being invoked and watchers are |
|
|
3668 | created/added/removed. |
|
|
3669 | |
|
|
3670 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3671 | which uses exactly this technique (which is suited for many high-level |
|
|
3672 | languages). |
|
|
3673 | |
|
|
3674 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3675 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3676 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3677 | |
|
|
3678 | First, you need to associate some data with the event loop: |
|
|
3679 | |
|
|
3680 | typedef struct { |
|
|
3681 | mutex_t lock; /* global loop lock */ |
|
|
3682 | ev_async async_w; |
|
|
3683 | thread_t tid; |
|
|
3684 | cond_t invoke_cv; |
|
|
3685 | } userdata; |
|
|
3686 | |
|
|
3687 | void prepare_loop (EV_P) |
|
|
3688 | { |
|
|
3689 | // for simplicity, we use a static userdata struct. |
|
|
3690 | static userdata u; |
|
|
3691 | |
|
|
3692 | ev_async_init (&u->async_w, async_cb); |
|
|
3693 | ev_async_start (EV_A_ &u->async_w); |
|
|
3694 | |
|
|
3695 | pthread_mutex_init (&u->lock, 0); |
|
|
3696 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3697 | |
|
|
3698 | // now associate this with the loop |
|
|
3699 | ev_set_userdata (EV_A_ u); |
|
|
3700 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3701 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3702 | |
|
|
3703 | // then create the thread running ev_run |
|
|
3704 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3705 | } |
|
|
3706 | |
|
|
3707 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3708 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3709 | that might have been added: |
|
|
3710 | |
|
|
3711 | static void |
|
|
3712 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3713 | { |
|
|
3714 | // just used for the side effects |
|
|
3715 | } |
|
|
3716 | |
|
|
3717 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3718 | protecting the loop data, respectively. |
|
|
3719 | |
|
|
3720 | static void |
|
|
3721 | l_release (EV_P) |
|
|
3722 | { |
|
|
3723 | userdata *u = ev_userdata (EV_A); |
|
|
3724 | pthread_mutex_unlock (&u->lock); |
|
|
3725 | } |
|
|
3726 | |
|
|
3727 | static void |
|
|
3728 | l_acquire (EV_P) |
|
|
3729 | { |
|
|
3730 | userdata *u = ev_userdata (EV_A); |
|
|
3731 | pthread_mutex_lock (&u->lock); |
|
|
3732 | } |
|
|
3733 | |
|
|
3734 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3735 | into C<ev_run>: |
|
|
3736 | |
|
|
3737 | void * |
|
|
3738 | l_run (void *thr_arg) |
|
|
3739 | { |
|
|
3740 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3741 | |
|
|
3742 | l_acquire (EV_A); |
|
|
3743 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3744 | ev_run (EV_A_ 0); |
|
|
3745 | l_release (EV_A); |
|
|
3746 | |
|
|
3747 | return 0; |
|
|
3748 | } |
|
|
3749 | |
|
|
3750 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3751 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3752 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3753 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3754 | and b) skipping inter-thread-communication when there are no pending |
|
|
3755 | watchers is very beneficial): |
|
|
3756 | |
|
|
3757 | static void |
|
|
3758 | l_invoke (EV_P) |
|
|
3759 | { |
|
|
3760 | userdata *u = ev_userdata (EV_A); |
|
|
3761 | |
|
|
3762 | while (ev_pending_count (EV_A)) |
|
|
3763 | { |
|
|
3764 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3765 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3766 | } |
|
|
3767 | } |
|
|
3768 | |
|
|
3769 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3770 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3771 | thread to continue: |
|
|
3772 | |
|
|
3773 | static void |
|
|
3774 | real_invoke_pending (EV_P) |
|
|
3775 | { |
|
|
3776 | userdata *u = ev_userdata (EV_A); |
|
|
3777 | |
|
|
3778 | pthread_mutex_lock (&u->lock); |
|
|
3779 | ev_invoke_pending (EV_A); |
|
|
3780 | pthread_cond_signal (&u->invoke_cv); |
|
|
3781 | pthread_mutex_unlock (&u->lock); |
|
|
3782 | } |
|
|
3783 | |
|
|
3784 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3785 | event loop, you will now have to lock: |
|
|
3786 | |
|
|
3787 | ev_timer timeout_watcher; |
|
|
3788 | userdata *u = ev_userdata (EV_A); |
|
|
3789 | |
|
|
3790 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3791 | |
|
|
3792 | pthread_mutex_lock (&u->lock); |
|
|
3793 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3794 | ev_async_send (EV_A_ &u->async_w); |
|
|
3795 | pthread_mutex_unlock (&u->lock); |
|
|
3796 | |
|
|
3797 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3798 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3799 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3800 | watchers in the next event loop iteration. |
|
|
3801 | |
|
|
3802 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3803 | |
|
|
3804 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3805 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3806 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3807 | doesn't need callbacks anymore. |
|
|
3808 | |
|
|
3809 | Imagine you have coroutines that you can switch to using a function |
|
|
3810 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3811 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3812 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3813 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3814 | the differing C<;> conventions): |
|
|
3815 | |
|
|
3816 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3817 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3818 | |
|
|
3819 | That means instead of having a C callback function, you store the |
|
|
3820 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3821 | your callback, you instead have it switch to that coroutine. |
|
|
3822 | |
|
|
3823 | A coroutine might now wait for an event with a function called |
|
|
3824 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3825 | matter when, or whether the watcher is active or not when this function is |
|
|
3826 | called): |
|
|
3827 | |
|
|
3828 | void |
|
|
3829 | wait_for_event (ev_watcher *w) |
|
|
3830 | { |
|
|
3831 | ev_cb_set (w) = current_coro; |
|
|
3832 | switch_to (libev_coro); |
|
|
3833 | } |
|
|
3834 | |
|
|
3835 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3836 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3837 | this or any other coroutine. |
|
|
3838 | |
|
|
3839 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3840 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3841 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3842 | any waiters. |
|
|
3843 | |
|
|
3844 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3845 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3846 | |
|
|
3847 | // my_ev.h |
|
|
3848 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3849 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3850 | #include "../libev/ev.h" |
|
|
3851 | |
|
|
3852 | // my_ev.c |
|
|
3853 | #define EV_H "my_ev.h" |
|
|
3854 | #include "../libev/ev.c" |
|
|
3855 | |
|
|
3856 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3857 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3858 | can even use F<ev.h> as header file name directly. |
2320 | |
3859 | |
2321 | |
3860 | |
2322 | =head1 LIBEVENT EMULATION |
3861 | =head1 LIBEVENT EMULATION |
2323 | |
3862 | |
2324 | Libev offers a compatibility emulation layer for libevent. It cannot |
3863 | Libev offers a compatibility emulation layer for libevent. It cannot |
2325 | emulate the internals of libevent, so here are some usage hints: |
3864 | emulate the internals of libevent, so here are some usage hints: |
2326 | |
3865 | |
2327 | =over 4 |
3866 | =over 4 |
|
|
3867 | |
|
|
3868 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3869 | |
|
|
3870 | This was the newest libevent version available when libev was implemented, |
|
|
3871 | and is still mostly unchanged in 2010. |
2328 | |
3872 | |
2329 | =item * Use it by including <event.h>, as usual. |
3873 | =item * Use it by including <event.h>, as usual. |
2330 | |
3874 | |
2331 | =item * The following members are fully supported: ev_base, ev_callback, |
3875 | =item * The following members are fully supported: ev_base, ev_callback, |
2332 | ev_arg, ev_fd, ev_res, ev_events. |
3876 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2337 | |
3881 | |
2338 | =item * Priorities are not currently supported. Initialising priorities |
3882 | =item * Priorities are not currently supported. Initialising priorities |
2339 | will fail and all watchers will have the same priority, even though there |
3883 | will fail and all watchers will have the same priority, even though there |
2340 | is an ev_pri field. |
3884 | is an ev_pri field. |
2341 | |
3885 | |
|
|
3886 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
3887 | base that registered the signal gets the signals. |
|
|
3888 | |
2342 | =item * Other members are not supported. |
3889 | =item * Other members are not supported. |
2343 | |
3890 | |
2344 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3891 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2345 | to use the libev header file and library. |
3892 | to use the libev header file and library. |
2346 | |
3893 | |
2347 | =back |
3894 | =back |
2348 | |
3895 | |
2349 | =head1 C++ SUPPORT |
3896 | =head1 C++ SUPPORT |
2350 | |
3897 | |
2351 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3898 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2352 | you to use some convinience methods to start/stop watchers and also change |
3899 | you to use some convenience methods to start/stop watchers and also change |
2353 | the callback model to a model using method callbacks on objects. |
3900 | the callback model to a model using method callbacks on objects. |
2354 | |
3901 | |
2355 | To use it, |
3902 | To use it, |
2356 | |
3903 | |
2357 | #include <ev++.h> |
3904 | #include <ev++.h> |
2358 | |
3905 | |
2359 | This automatically includes F<ev.h> and puts all of its definitions (many |
3906 | This automatically includes F<ev.h> and puts all of its definitions (many |
2360 | of them macros) into the global namespace. All C++ specific things are |
3907 | of them macros) into the global namespace. All C++ specific things are |
2361 | put into the C<ev> namespace. It should support all the same embedding |
3908 | put into the C<ev> namespace. It should support all the same embedding |
2362 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
3909 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
2364 | Care has been taken to keep the overhead low. The only data member the C++ |
3911 | Care has been taken to keep the overhead low. The only data member the C++ |
2365 | classes add (compared to plain C-style watchers) is the event loop pointer |
3912 | classes add (compared to plain C-style watchers) is the event loop pointer |
2366 | that the watcher is associated with (or no additional members at all if |
3913 | that the watcher is associated with (or no additional members at all if |
2367 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3914 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2368 | |
3915 | |
2369 | Currently, functions, and static and non-static member functions can be |
3916 | Currently, functions, static and non-static member functions and classes |
2370 | used as callbacks. Other types should be easy to add as long as they only |
3917 | with C<operator ()> can be used as callbacks. Other types should be easy |
2371 | need one additional pointer for context. If you need support for other |
3918 | to add as long as they only need one additional pointer for context. If |
2372 | types of functors please contact the author (preferably after implementing |
3919 | you need support for other types of functors please contact the author |
2373 | it). |
3920 | (preferably after implementing it). |
2374 | |
3921 | |
2375 | Here is a list of things available in the C<ev> namespace: |
3922 | Here is a list of things available in the C<ev> namespace: |
2376 | |
3923 | |
2377 | =over 4 |
3924 | =over 4 |
2378 | |
3925 | |
… | |
… | |
2388 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3935 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
2389 | |
3936 | |
2390 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3937 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
2391 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3938 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
2392 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3939 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
2393 | defines by many implementations. |
3940 | defined by many implementations. |
2394 | |
3941 | |
2395 | All of those classes have these methods: |
3942 | All of those classes have these methods: |
2396 | |
3943 | |
2397 | =over 4 |
3944 | =over 4 |
2398 | |
3945 | |
2399 | =item ev::TYPE::TYPE () |
3946 | =item ev::TYPE::TYPE () |
2400 | |
3947 | |
2401 | =item ev::TYPE::TYPE (struct ev_loop *) |
3948 | =item ev::TYPE::TYPE (loop) |
2402 | |
3949 | |
2403 | =item ev::TYPE::~TYPE |
3950 | =item ev::TYPE::~TYPE |
2404 | |
3951 | |
2405 | The constructor (optionally) takes an event loop to associate the watcher |
3952 | The constructor (optionally) takes an event loop to associate the watcher |
2406 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3953 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2429 | your compiler is good :), then the method will be fully inlined into the |
3976 | your compiler is good :), then the method will be fully inlined into the |
2430 | thunking function, making it as fast as a direct C callback. |
3977 | thunking function, making it as fast as a direct C callback. |
2431 | |
3978 | |
2432 | Example: simple class declaration and watcher initialisation |
3979 | Example: simple class declaration and watcher initialisation |
2433 | |
3980 | |
2434 | struct myclass |
3981 | struct myclass |
2435 | { |
3982 | { |
2436 | void io_cb (ev::io &w, int revents) { } |
3983 | void io_cb (ev::io &w, int revents) { } |
2437 | } |
3984 | } |
2438 | |
3985 | |
2439 | myclass obj; |
3986 | myclass obj; |
2440 | ev::io iow; |
3987 | ev::io iow; |
2441 | iow.set <myclass, &myclass::io_cb> (&obj); |
3988 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3989 | |
|
|
3990 | =item w->set (object *) |
|
|
3991 | |
|
|
3992 | This is a variation of a method callback - leaving out the method to call |
|
|
3993 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3994 | functor objects without having to manually specify the C<operator ()> all |
|
|
3995 | the time. Incidentally, you can then also leave out the template argument |
|
|
3996 | list. |
|
|
3997 | |
|
|
3998 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3999 | int revents)>. |
|
|
4000 | |
|
|
4001 | See the method-C<set> above for more details. |
|
|
4002 | |
|
|
4003 | Example: use a functor object as callback. |
|
|
4004 | |
|
|
4005 | struct myfunctor |
|
|
4006 | { |
|
|
4007 | void operator() (ev::io &w, int revents) |
|
|
4008 | { |
|
|
4009 | ... |
|
|
4010 | } |
|
|
4011 | } |
|
|
4012 | |
|
|
4013 | myfunctor f; |
|
|
4014 | |
|
|
4015 | ev::io w; |
|
|
4016 | w.set (&f); |
2442 | |
4017 | |
2443 | =item w->set<function> (void *data = 0) |
4018 | =item w->set<function> (void *data = 0) |
2444 | |
4019 | |
2445 | Also sets a callback, but uses a static method or plain function as |
4020 | Also sets a callback, but uses a static method or plain function as |
2446 | callback. The optional C<data> argument will be stored in the watcher's |
4021 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2448 | |
4023 | |
2449 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
4024 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2450 | |
4025 | |
2451 | See the method-C<set> above for more details. |
4026 | See the method-C<set> above for more details. |
2452 | |
4027 | |
2453 | Example: |
4028 | Example: Use a plain function as callback. |
2454 | |
4029 | |
2455 | static void io_cb (ev::io &w, int revents) { } |
4030 | static void io_cb (ev::io &w, int revents) { } |
2456 | iow.set <io_cb> (); |
4031 | iow.set <io_cb> (); |
2457 | |
4032 | |
2458 | =item w->set (struct ev_loop *) |
4033 | =item w->set (loop) |
2459 | |
4034 | |
2460 | Associates a different C<struct ev_loop> with this watcher. You can only |
4035 | Associates a different C<struct ev_loop> with this watcher. You can only |
2461 | do this when the watcher is inactive (and not pending either). |
4036 | do this when the watcher is inactive (and not pending either). |
2462 | |
4037 | |
2463 | =item w->set ([args]) |
4038 | =item w->set ([arguments]) |
2464 | |
4039 | |
2465 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
4040 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2466 | called at least once. Unlike the C counterpart, an active watcher gets |
4041 | method or a suitable start method must be called at least once. Unlike the |
2467 | automatically stopped and restarted when reconfiguring it with this |
4042 | C counterpart, an active watcher gets automatically stopped and restarted |
2468 | method. |
4043 | when reconfiguring it with this method. |
2469 | |
4044 | |
2470 | =item w->start () |
4045 | =item w->start () |
2471 | |
4046 | |
2472 | Starts the watcher. Note that there is no C<loop> argument, as the |
4047 | Starts the watcher. Note that there is no C<loop> argument, as the |
2473 | constructor already stores the event loop. |
4048 | constructor already stores the event loop. |
2474 | |
4049 | |
|
|
4050 | =item w->start ([arguments]) |
|
|
4051 | |
|
|
4052 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4053 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4054 | the configure C<set> method of the watcher. |
|
|
4055 | |
2475 | =item w->stop () |
4056 | =item w->stop () |
2476 | |
4057 | |
2477 | Stops the watcher if it is active. Again, no C<loop> argument. |
4058 | Stops the watcher if it is active. Again, no C<loop> argument. |
2478 | |
4059 | |
2479 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4060 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2491 | |
4072 | |
2492 | =back |
4073 | =back |
2493 | |
4074 | |
2494 | =back |
4075 | =back |
2495 | |
4076 | |
2496 | Example: Define a class with an IO and idle watcher, start one of them in |
4077 | Example: Define a class with two I/O and idle watchers, start the I/O |
2497 | the constructor. |
4078 | watchers in the constructor. |
2498 | |
4079 | |
2499 | class myclass |
4080 | class myclass |
2500 | { |
4081 | { |
2501 | ev::io io; void io_cb (ev::io &w, int revents); |
4082 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4083 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
2502 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
4084 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2503 | |
4085 | |
2504 | myclass (int fd) |
4086 | myclass (int fd) |
2505 | { |
4087 | { |
2506 | io .set <myclass, &myclass::io_cb > (this); |
4088 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4089 | io2 .set <myclass, &myclass::io2_cb > (this); |
2507 | idle.set <myclass, &myclass::idle_cb> (this); |
4090 | idle.set <myclass, &myclass::idle_cb> (this); |
2508 | |
4091 | |
2509 | io.start (fd, ev::READ); |
4092 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4093 | io.start (); // start it whenever convenient |
|
|
4094 | |
|
|
4095 | io2.start (fd, ev::READ); // set + start in one call |
2510 | } |
4096 | } |
2511 | }; |
4097 | }; |
2512 | |
4098 | |
2513 | |
4099 | |
2514 | =head1 OTHER LANGUAGE BINDINGS |
4100 | =head1 OTHER LANGUAGE BINDINGS |
2515 | |
4101 | |
2516 | Libev does not offer other language bindings itself, but bindings for a |
4102 | Libev does not offer other language bindings itself, but bindings for a |
2517 | numbe rof languages exist in the form of third-party packages. If you know |
4103 | number of languages exist in the form of third-party packages. If you know |
2518 | any interesting language binding in addition to the ones listed here, drop |
4104 | any interesting language binding in addition to the ones listed here, drop |
2519 | me a note. |
4105 | me a note. |
2520 | |
4106 | |
2521 | =over 4 |
4107 | =over 4 |
2522 | |
4108 | |
2523 | =item Perl |
4109 | =item Perl |
2524 | |
4110 | |
2525 | The EV module implements the full libev API and is actually used to test |
4111 | The EV module implements the full libev API and is actually used to test |
2526 | libev. EV is developed together with libev. Apart from the EV core module, |
4112 | libev. EV is developed together with libev. Apart from the EV core module, |
2527 | there are additional modules that implement libev-compatible interfaces |
4113 | there are additional modules that implement libev-compatible interfaces |
2528 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
4114 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2529 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
4115 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
4116 | and C<EV::Glib>). |
2530 | |
4117 | |
2531 | It can be found and installed via CPAN, its homepage is found at |
4118 | It can be found and installed via CPAN, its homepage is at |
2532 | L<http://software.schmorp.de/pkg/EV>. |
4119 | L<http://software.schmorp.de/pkg/EV>. |
2533 | |
4120 | |
|
|
4121 | =item Python |
|
|
4122 | |
|
|
4123 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
4124 | seems to be quite complete and well-documented. |
|
|
4125 | |
2534 | =item Ruby |
4126 | =item Ruby |
2535 | |
4127 | |
2536 | Tony Arcieri has written a ruby extension that offers access to a subset |
4128 | Tony Arcieri has written a ruby extension that offers access to a subset |
2537 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
4129 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2538 | more on top of it. It can be found via gem servers. Its homepage is at |
4130 | more on top of it. It can be found via gem servers. Its homepage is at |
2539 | L<http://rev.rubyforge.org/>. |
4131 | L<http://rev.rubyforge.org/>. |
2540 | |
4132 | |
|
|
4133 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
4134 | makes rev work even on mingw. |
|
|
4135 | |
|
|
4136 | =item Haskell |
|
|
4137 | |
|
|
4138 | A haskell binding to libev is available at |
|
|
4139 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
4140 | |
2541 | =item D |
4141 | =item D |
2542 | |
4142 | |
2543 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4143 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2544 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
4144 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
|
|
4145 | |
|
|
4146 | =item Ocaml |
|
|
4147 | |
|
|
4148 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
4149 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4150 | |
|
|
4151 | =item Lua |
|
|
4152 | |
|
|
4153 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4154 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4155 | L<http://github.com/brimworks/lua-ev>. |
2545 | |
4156 | |
2546 | =back |
4157 | =back |
2547 | |
4158 | |
2548 | |
4159 | |
2549 | =head1 MACRO MAGIC |
4160 | =head1 MACRO MAGIC |
2550 | |
4161 | |
2551 | Libev can be compiled with a variety of options, the most fundamantal |
4162 | Libev can be compiled with a variety of options, the most fundamental |
2552 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
4163 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2553 | functions and callbacks have an initial C<struct ev_loop *> argument. |
4164 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2554 | |
4165 | |
2555 | To make it easier to write programs that cope with either variant, the |
4166 | To make it easier to write programs that cope with either variant, the |
2556 | following macros are defined: |
4167 | following macros are defined: |
… | |
… | |
2561 | |
4172 | |
2562 | This provides the loop I<argument> for functions, if one is required ("ev |
4173 | This provides the loop I<argument> for functions, if one is required ("ev |
2563 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4174 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2564 | C<EV_A_> is used when other arguments are following. Example: |
4175 | C<EV_A_> is used when other arguments are following. Example: |
2565 | |
4176 | |
2566 | ev_unref (EV_A); |
4177 | ev_unref (EV_A); |
2567 | ev_timer_add (EV_A_ watcher); |
4178 | ev_timer_add (EV_A_ watcher); |
2568 | ev_loop (EV_A_ 0); |
4179 | ev_run (EV_A_ 0); |
2569 | |
4180 | |
2570 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4181 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2571 | which is often provided by the following macro. |
4182 | which is often provided by the following macro. |
2572 | |
4183 | |
2573 | =item C<EV_P>, C<EV_P_> |
4184 | =item C<EV_P>, C<EV_P_> |
2574 | |
4185 | |
2575 | This provides the loop I<parameter> for functions, if one is required ("ev |
4186 | This provides the loop I<parameter> for functions, if one is required ("ev |
2576 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
4187 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
2577 | C<EV_P_> is used when other parameters are following. Example: |
4188 | C<EV_P_> is used when other parameters are following. Example: |
2578 | |
4189 | |
2579 | // this is how ev_unref is being declared |
4190 | // this is how ev_unref is being declared |
2580 | static void ev_unref (EV_P); |
4191 | static void ev_unref (EV_P); |
2581 | |
4192 | |
2582 | // this is how you can declare your typical callback |
4193 | // this is how you can declare your typical callback |
2583 | static void cb (EV_P_ ev_timer *w, int revents) |
4194 | static void cb (EV_P_ ev_timer *w, int revents) |
2584 | |
4195 | |
2585 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
4196 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
2586 | suitable for use with C<EV_A>. |
4197 | suitable for use with C<EV_A>. |
2587 | |
4198 | |
2588 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4199 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2589 | |
4200 | |
2590 | Similar to the other two macros, this gives you the value of the default |
4201 | Similar to the other two macros, this gives you the value of the default |
2591 | loop, if multiple loops are supported ("ev loop default"). |
4202 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4203 | will be initialised if it isn't already initialised. |
|
|
4204 | |
|
|
4205 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4206 | to initialise the loop somewhere. |
|
|
4207 | |
|
|
4208 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
4209 | |
|
|
4210 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
4211 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
4212 | is undefined when the default loop has not been initialised by a previous |
|
|
4213 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
4214 | |
|
|
4215 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
4216 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2592 | |
4217 | |
2593 | =back |
4218 | =back |
2594 | |
4219 | |
2595 | Example: Declare and initialise a check watcher, utilising the above |
4220 | Example: Declare and initialise a check watcher, utilising the above |
2596 | macros so it will work regardless of whether multiple loops are supported |
4221 | macros so it will work regardless of whether multiple loops are supported |
2597 | or not. |
4222 | or not. |
2598 | |
4223 | |
2599 | static void |
4224 | static void |
2600 | check_cb (EV_P_ ev_timer *w, int revents) |
4225 | check_cb (EV_P_ ev_timer *w, int revents) |
2601 | { |
4226 | { |
2602 | ev_check_stop (EV_A_ w); |
4227 | ev_check_stop (EV_A_ w); |
2603 | } |
4228 | } |
2604 | |
4229 | |
2605 | ev_check check; |
4230 | ev_check check; |
2606 | ev_check_init (&check, check_cb); |
4231 | ev_check_init (&check, check_cb); |
2607 | ev_check_start (EV_DEFAULT_ &check); |
4232 | ev_check_start (EV_DEFAULT_ &check); |
2608 | ev_loop (EV_DEFAULT_ 0); |
4233 | ev_run (EV_DEFAULT_ 0); |
2609 | |
4234 | |
2610 | =head1 EMBEDDING |
4235 | =head1 EMBEDDING |
2611 | |
4236 | |
2612 | Libev can (and often is) directly embedded into host |
4237 | Libev can (and often is) directly embedded into host |
2613 | applications. Examples of applications that embed it include the Deliantra |
4238 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2620 | libev somewhere in your source tree). |
4245 | libev somewhere in your source tree). |
2621 | |
4246 | |
2622 | =head2 FILESETS |
4247 | =head2 FILESETS |
2623 | |
4248 | |
2624 | Depending on what features you need you need to include one or more sets of files |
4249 | Depending on what features you need you need to include one or more sets of files |
2625 | in your app. |
4250 | in your application. |
2626 | |
4251 | |
2627 | =head3 CORE EVENT LOOP |
4252 | =head3 CORE EVENT LOOP |
2628 | |
4253 | |
2629 | To include only the libev core (all the C<ev_*> functions), with manual |
4254 | To include only the libev core (all the C<ev_*> functions), with manual |
2630 | configuration (no autoconf): |
4255 | configuration (no autoconf): |
2631 | |
4256 | |
2632 | #define EV_STANDALONE 1 |
4257 | #define EV_STANDALONE 1 |
2633 | #include "ev.c" |
4258 | #include "ev.c" |
2634 | |
4259 | |
2635 | This will automatically include F<ev.h>, too, and should be done in a |
4260 | This will automatically include F<ev.h>, too, and should be done in a |
2636 | single C source file only to provide the function implementations. To use |
4261 | single C source file only to provide the function implementations. To use |
2637 | it, do the same for F<ev.h> in all files wishing to use this API (best |
4262 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2638 | done by writing a wrapper around F<ev.h> that you can include instead and |
4263 | done by writing a wrapper around F<ev.h> that you can include instead and |
2639 | where you can put other configuration options): |
4264 | where you can put other configuration options): |
2640 | |
4265 | |
2641 | #define EV_STANDALONE 1 |
4266 | #define EV_STANDALONE 1 |
2642 | #include "ev.h" |
4267 | #include "ev.h" |
2643 | |
4268 | |
2644 | Both header files and implementation files can be compiled with a C++ |
4269 | Both header files and implementation files can be compiled with a C++ |
2645 | compiler (at least, thats a stated goal, and breakage will be treated |
4270 | compiler (at least, that's a stated goal, and breakage will be treated |
2646 | as a bug). |
4271 | as a bug). |
2647 | |
4272 | |
2648 | You need the following files in your source tree, or in a directory |
4273 | You need the following files in your source tree, or in a directory |
2649 | in your include path (e.g. in libev/ when using -Ilibev): |
4274 | in your include path (e.g. in libev/ when using -Ilibev): |
2650 | |
4275 | |
2651 | ev.h |
4276 | ev.h |
2652 | ev.c |
4277 | ev.c |
2653 | ev_vars.h |
4278 | ev_vars.h |
2654 | ev_wrap.h |
4279 | ev_wrap.h |
2655 | |
4280 | |
2656 | ev_win32.c required on win32 platforms only |
4281 | ev_win32.c required on win32 platforms only |
2657 | |
4282 | |
2658 | ev_select.c only when select backend is enabled (which is enabled by default) |
4283 | ev_select.c only when select backend is enabled (which is enabled by default) |
2659 | ev_poll.c only when poll backend is enabled (disabled by default) |
4284 | ev_poll.c only when poll backend is enabled (disabled by default) |
2660 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4285 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2661 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4286 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2662 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4287 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2663 | |
4288 | |
2664 | F<ev.c> includes the backend files directly when enabled, so you only need |
4289 | F<ev.c> includes the backend files directly when enabled, so you only need |
2665 | to compile this single file. |
4290 | to compile this single file. |
2666 | |
4291 | |
2667 | =head3 LIBEVENT COMPATIBILITY API |
4292 | =head3 LIBEVENT COMPATIBILITY API |
2668 | |
4293 | |
2669 | To include the libevent compatibility API, also include: |
4294 | To include the libevent compatibility API, also include: |
2670 | |
4295 | |
2671 | #include "event.c" |
4296 | #include "event.c" |
2672 | |
4297 | |
2673 | in the file including F<ev.c>, and: |
4298 | in the file including F<ev.c>, and: |
2674 | |
4299 | |
2675 | #include "event.h" |
4300 | #include "event.h" |
2676 | |
4301 | |
2677 | in the files that want to use the libevent API. This also includes F<ev.h>. |
4302 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2678 | |
4303 | |
2679 | You need the following additional files for this: |
4304 | You need the following additional files for this: |
2680 | |
4305 | |
2681 | event.h |
4306 | event.h |
2682 | event.c |
4307 | event.c |
2683 | |
4308 | |
2684 | =head3 AUTOCONF SUPPORT |
4309 | =head3 AUTOCONF SUPPORT |
2685 | |
4310 | |
2686 | Instead of using C<EV_STANDALONE=1> and providing your config in |
4311 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2687 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
4312 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2688 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
4313 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2689 | include F<config.h> and configure itself accordingly. |
4314 | include F<config.h> and configure itself accordingly. |
2690 | |
4315 | |
2691 | For this of course you need the m4 file: |
4316 | For this of course you need the m4 file: |
2692 | |
4317 | |
2693 | libev.m4 |
4318 | libev.m4 |
2694 | |
4319 | |
2695 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4320 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2696 | |
4321 | |
2697 | Libev can be configured via a variety of preprocessor symbols you have to define |
4322 | Libev can be configured via a variety of preprocessor symbols you have to |
2698 | before including any of its files. The default is not to build for multiplicity |
4323 | define before including (or compiling) any of its files. The default in |
2699 | and only include the select backend. |
4324 | the absence of autoconf is documented for every option. |
|
|
4325 | |
|
|
4326 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4327 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4328 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4329 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4330 | users of libev and the libev code itself must be compiled with compatible |
|
|
4331 | settings. |
2700 | |
4332 | |
2701 | =over 4 |
4333 | =over 4 |
2702 | |
4334 | |
|
|
4335 | =item EV_COMPAT3 (h) |
|
|
4336 | |
|
|
4337 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4338 | release of libev comes with wrappers for the functions and symbols that |
|
|
4339 | have been renamed between libev version 3 and 4. |
|
|
4340 | |
|
|
4341 | You can disable these wrappers (to test compatibility with future |
|
|
4342 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4343 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4344 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4345 | typedef in that case. |
|
|
4346 | |
|
|
4347 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4348 | and in some even more future version the compatibility code will be |
|
|
4349 | removed completely. |
|
|
4350 | |
2703 | =item EV_STANDALONE |
4351 | =item EV_STANDALONE (h) |
2704 | |
4352 | |
2705 | Must always be C<1> if you do not use autoconf configuration, which |
4353 | Must always be C<1> if you do not use autoconf configuration, which |
2706 | keeps libev from including F<config.h>, and it also defines dummy |
4354 | keeps libev from including F<config.h>, and it also defines dummy |
2707 | implementations for some libevent functions (such as logging, which is not |
4355 | implementations for some libevent functions (such as logging, which is not |
2708 | supported). It will also not define any of the structs usually found in |
4356 | supported). It will also not define any of the structs usually found in |
2709 | F<event.h> that are not directly supported by the libev core alone. |
4357 | F<event.h> that are not directly supported by the libev core alone. |
2710 | |
4358 | |
|
|
4359 | In standalone mode, libev will still try to automatically deduce the |
|
|
4360 | configuration, but has to be more conservative. |
|
|
4361 | |
|
|
4362 | =item EV_USE_FLOOR |
|
|
4363 | |
|
|
4364 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4365 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4366 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4367 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4368 | function is not available will fail, so the safe default is to not enable |
|
|
4369 | this. |
|
|
4370 | |
2711 | =item EV_USE_MONOTONIC |
4371 | =item EV_USE_MONOTONIC |
2712 | |
4372 | |
2713 | If defined to be C<1>, libev will try to detect the availability of the |
4373 | If defined to be C<1>, libev will try to detect the availability of the |
2714 | monotonic clock option at both compiletime and runtime. Otherwise no use |
4374 | monotonic clock option at both compile time and runtime. Otherwise no |
2715 | of the monotonic clock option will be attempted. If you enable this, you |
4375 | use of the monotonic clock option will be attempted. If you enable this, |
2716 | usually have to link against librt or something similar. Enabling it when |
4376 | you usually have to link against librt or something similar. Enabling it |
2717 | the functionality isn't available is safe, though, although you have |
4377 | when the functionality isn't available is safe, though, although you have |
2718 | to make sure you link against any libraries where the C<clock_gettime> |
4378 | to make sure you link against any libraries where the C<clock_gettime> |
2719 | function is hiding in (often F<-lrt>). |
4379 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2720 | |
4380 | |
2721 | =item EV_USE_REALTIME |
4381 | =item EV_USE_REALTIME |
2722 | |
4382 | |
2723 | If defined to be C<1>, libev will try to detect the availability of the |
4383 | If defined to be C<1>, libev will try to detect the availability of the |
2724 | realtime clock option at compiletime (and assume its availability at |
4384 | real-time clock option at compile time (and assume its availability |
2725 | runtime if successful). Otherwise no use of the realtime clock option will |
4385 | at runtime if successful). Otherwise no use of the real-time clock |
2726 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
4386 | option will be attempted. This effectively replaces C<gettimeofday> |
2727 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
4387 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2728 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
4388 | correctness. See the note about libraries in the description of |
|
|
4389 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
4390 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
4391 | |
|
|
4392 | =item EV_USE_CLOCK_SYSCALL |
|
|
4393 | |
|
|
4394 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
4395 | of calling the system-provided C<clock_gettime> function. This option |
|
|
4396 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
4397 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
4398 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4399 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4400 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
4401 | higher, as it simplifies linking (no need for C<-lrt>). |
2729 | |
4402 | |
2730 | =item EV_USE_NANOSLEEP |
4403 | =item EV_USE_NANOSLEEP |
2731 | |
4404 | |
2732 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
4405 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2733 | and will use it for delays. Otherwise it will use C<select ()>. |
4406 | and will use it for delays. Otherwise it will use C<select ()>. |
2734 | |
4407 | |
|
|
4408 | =item EV_USE_EVENTFD |
|
|
4409 | |
|
|
4410 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4411 | available and will probe for kernel support at runtime. This will improve |
|
|
4412 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4413 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4414 | 2.7 or newer, otherwise disabled. |
|
|
4415 | |
2735 | =item EV_USE_SELECT |
4416 | =item EV_USE_SELECT |
2736 | |
4417 | |
2737 | If undefined or defined to be C<1>, libev will compile in support for the |
4418 | If undefined or defined to be C<1>, libev will compile in support for the |
2738 | C<select>(2) backend. No attempt at autodetection will be done: if no |
4419 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
2739 | other method takes over, select will be it. Otherwise the select backend |
4420 | other method takes over, select will be it. Otherwise the select backend |
2740 | will not be compiled in. |
4421 | will not be compiled in. |
2741 | |
4422 | |
2742 | =item EV_SELECT_USE_FD_SET |
4423 | =item EV_SELECT_USE_FD_SET |
2743 | |
4424 | |
2744 | If defined to C<1>, then the select backend will use the system C<fd_set> |
4425 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2745 | structure. This is useful if libev doesn't compile due to a missing |
4426 | structure. This is useful if libev doesn't compile due to a missing |
2746 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
4427 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2747 | exotic systems. This usually limits the range of file descriptors to some |
4428 | on exotic systems. This usually limits the range of file descriptors to |
2748 | low limit such as 1024 or might have other limitations (winsocket only |
4429 | some low limit such as 1024 or might have other limitations (winsocket |
2749 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
4430 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2750 | influence the size of the C<fd_set> used. |
4431 | configures the maximum size of the C<fd_set>. |
2751 | |
4432 | |
2752 | =item EV_SELECT_IS_WINSOCKET |
4433 | =item EV_SELECT_IS_WINSOCKET |
2753 | |
4434 | |
2754 | When defined to C<1>, the select backend will assume that |
4435 | When defined to C<1>, the select backend will assume that |
2755 | select/socket/connect etc. don't understand file descriptors but |
4436 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2757 | be used is the winsock select). This means that it will call |
4438 | be used is the winsock select). This means that it will call |
2758 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4439 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2759 | it is assumed that all these functions actually work on fds, even |
4440 | it is assumed that all these functions actually work on fds, even |
2760 | on win32. Should not be defined on non-win32 platforms. |
4441 | on win32. Should not be defined on non-win32 platforms. |
2761 | |
4442 | |
2762 | =item EV_FD_TO_WIN32_HANDLE |
4443 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2763 | |
4444 | |
2764 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4445 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2765 | file descriptors to socket handles. When not defining this symbol (the |
4446 | file descriptors to socket handles. When not defining this symbol (the |
2766 | default), then libev will call C<_get_osfhandle>, which is usually |
4447 | default), then libev will call C<_get_osfhandle>, which is usually |
2767 | correct. In some cases, programs use their own file descriptor management, |
4448 | correct. In some cases, programs use their own file descriptor management, |
2768 | in which case they can provide this function to map fds to socket handles. |
4449 | in which case they can provide this function to map fds to socket handles. |
2769 | |
4450 | |
|
|
4451 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4452 | |
|
|
4453 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4454 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4455 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4456 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4457 | |
|
|
4458 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4459 | |
|
|
4460 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4461 | macro can be used to override the C<close> function, useful to unregister |
|
|
4462 | file descriptors again. Note that the replacement function has to close |
|
|
4463 | the underlying OS handle. |
|
|
4464 | |
2770 | =item EV_USE_POLL |
4465 | =item EV_USE_POLL |
2771 | |
4466 | |
2772 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4467 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2773 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4468 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2774 | takes precedence over select. |
4469 | takes precedence over select. |
2775 | |
4470 | |
2776 | =item EV_USE_EPOLL |
4471 | =item EV_USE_EPOLL |
2777 | |
4472 | |
2778 | If defined to be C<1>, libev will compile in support for the Linux |
4473 | If defined to be C<1>, libev will compile in support for the Linux |
2779 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4474 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2780 | otherwise another method will be used as fallback. This is the |
4475 | otherwise another method will be used as fallback. This is the preferred |
2781 | preferred backend for GNU/Linux systems. |
4476 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
4477 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2782 | |
4478 | |
2783 | =item EV_USE_KQUEUE |
4479 | =item EV_USE_KQUEUE |
2784 | |
4480 | |
2785 | If defined to be C<1>, libev will compile in support for the BSD style |
4481 | If defined to be C<1>, libev will compile in support for the BSD style |
2786 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4482 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2799 | otherwise another method will be used as fallback. This is the preferred |
4495 | otherwise another method will be used as fallback. This is the preferred |
2800 | backend for Solaris 10 systems. |
4496 | backend for Solaris 10 systems. |
2801 | |
4497 | |
2802 | =item EV_USE_DEVPOLL |
4498 | =item EV_USE_DEVPOLL |
2803 | |
4499 | |
2804 | reserved for future expansion, works like the USE symbols above. |
4500 | Reserved for future expansion, works like the USE symbols above. |
2805 | |
4501 | |
2806 | =item EV_USE_INOTIFY |
4502 | =item EV_USE_INOTIFY |
2807 | |
4503 | |
2808 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4504 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2809 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4505 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2810 | be detected at runtime. |
4506 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
4507 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2811 | |
4508 | |
2812 | =item EV_ATOMIC_T |
4509 | =item EV_ATOMIC_T |
2813 | |
4510 | |
2814 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4511 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2815 | access is atomic with respect to other threads or signal contexts. No such |
4512 | access is atomic and serialised with respect to other threads or signal |
2816 | type is easily found in the C language, so you can provide your own type |
4513 | contexts. No such type is easily found in the C language, so you can |
2817 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4514 | provide your own type that you know is safe for your purposes. It is used |
2818 | as well as for signal and thread safety in C<ev_async> watchers. |
4515 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4516 | in C<ev_async> watchers. |
2819 | |
4517 | |
2820 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
4518 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2821 | (from F<signal.h>), which is usually good enough on most platforms. |
4519 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4520 | although strictly speaking using a type that also implies a memory fence |
|
|
4521 | is required. |
2822 | |
4522 | |
2823 | =item EV_H |
4523 | =item EV_H (h) |
2824 | |
4524 | |
2825 | The name of the F<ev.h> header file used to include it. The default if |
4525 | The name of the F<ev.h> header file used to include it. The default if |
2826 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4526 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2827 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4527 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2828 | |
4528 | |
2829 | =item EV_CONFIG_H |
4529 | =item EV_CONFIG_H (h) |
2830 | |
4530 | |
2831 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4531 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2832 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4532 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2833 | C<EV_H>, above. |
4533 | C<EV_H>, above. |
2834 | |
4534 | |
2835 | =item EV_EVENT_H |
4535 | =item EV_EVENT_H (h) |
2836 | |
4536 | |
2837 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4537 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2838 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4538 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2839 | |
4539 | |
2840 | =item EV_PROTOTYPES |
4540 | =item EV_PROTOTYPES (h) |
2841 | |
4541 | |
2842 | If defined to be C<0>, then F<ev.h> will not define any function |
4542 | If defined to be C<0>, then F<ev.h> will not define any function |
2843 | prototypes, but still define all the structs and other symbols. This is |
4543 | prototypes, but still define all the structs and other symbols. This is |
2844 | occasionally useful if you want to provide your own wrapper functions |
4544 | occasionally useful if you want to provide your own wrapper functions |
2845 | around libev functions. |
4545 | around libev functions. |
… | |
… | |
2850 | will have the C<struct ev_loop *> as first argument, and you can create |
4550 | will have the C<struct ev_loop *> as first argument, and you can create |
2851 | additional independent event loops. Otherwise there will be no support |
4551 | additional independent event loops. Otherwise there will be no support |
2852 | for multiple event loops and there is no first event loop pointer |
4552 | for multiple event loops and there is no first event loop pointer |
2853 | argument. Instead, all functions act on the single default loop. |
4553 | argument. Instead, all functions act on the single default loop. |
2854 | |
4554 | |
|
|
4555 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4556 | default loop when multiplicity is switched off - you always have to |
|
|
4557 | initialise the loop manually in this case. |
|
|
4558 | |
2855 | =item EV_MINPRI |
4559 | =item EV_MINPRI |
2856 | |
4560 | |
2857 | =item EV_MAXPRI |
4561 | =item EV_MAXPRI |
2858 | |
4562 | |
2859 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4563 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
2864 | When doing priority-based operations, libev usually has to linearly search |
4568 | When doing priority-based operations, libev usually has to linearly search |
2865 | all the priorities, so having many of them (hundreds) uses a lot of space |
4569 | all the priorities, so having many of them (hundreds) uses a lot of space |
2866 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
4570 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2867 | fine. |
4571 | fine. |
2868 | |
4572 | |
2869 | If your embedding app does not need any priorities, defining these both to |
4573 | If your embedding application does not need any priorities, defining these |
2870 | C<0> will save some memory and cpu. |
4574 | both to C<0> will save some memory and CPU. |
2871 | |
4575 | |
2872 | =item EV_PERIODIC_ENABLE |
4576 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4577 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4578 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
2873 | |
4579 | |
2874 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4580 | If undefined or defined to be C<1> (and the platform supports it), then |
2875 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4581 | the respective watcher type is supported. If defined to be C<0>, then it |
2876 | code. |
4582 | is not. Disabling watcher types mainly saves code size. |
2877 | |
4583 | |
2878 | =item EV_IDLE_ENABLE |
4584 | =item EV_FEATURES |
2879 | |
|
|
2880 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
2881 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
2882 | code. |
|
|
2883 | |
|
|
2884 | =item EV_EMBED_ENABLE |
|
|
2885 | |
|
|
2886 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
2887 | defined to be C<0>, then they are not. |
|
|
2888 | |
|
|
2889 | =item EV_STAT_ENABLE |
|
|
2890 | |
|
|
2891 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
2892 | defined to be C<0>, then they are not. |
|
|
2893 | |
|
|
2894 | =item EV_FORK_ENABLE |
|
|
2895 | |
|
|
2896 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2897 | defined to be C<0>, then they are not. |
|
|
2898 | |
|
|
2899 | =item EV_ASYNC_ENABLE |
|
|
2900 | |
|
|
2901 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
2902 | defined to be C<0>, then they are not. |
|
|
2903 | |
|
|
2904 | =item EV_MINIMAL |
|
|
2905 | |
4585 | |
2906 | If you need to shave off some kilobytes of code at the expense of some |
4586 | If you need to shave off some kilobytes of code at the expense of some |
2907 | speed, define this symbol to C<1>. Currently only used for gcc to override |
4587 | speed (but with the full API), you can define this symbol to request |
2908 | some inlining decisions, saves roughly 30% codesize of amd64. |
4588 | certain subsets of functionality. The default is to enable all features |
|
|
4589 | that can be enabled on the platform. |
|
|
4590 | |
|
|
4591 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4592 | with some broad features you want) and then selectively re-enable |
|
|
4593 | additional parts you want, for example if you want everything minimal, |
|
|
4594 | but multiple event loop support, async and child watchers and the poll |
|
|
4595 | backend, use this: |
|
|
4596 | |
|
|
4597 | #define EV_FEATURES 0 |
|
|
4598 | #define EV_MULTIPLICITY 1 |
|
|
4599 | #define EV_USE_POLL 1 |
|
|
4600 | #define EV_CHILD_ENABLE 1 |
|
|
4601 | #define EV_ASYNC_ENABLE 1 |
|
|
4602 | |
|
|
4603 | The actual value is a bitset, it can be a combination of the following |
|
|
4604 | values: |
|
|
4605 | |
|
|
4606 | =over 4 |
|
|
4607 | |
|
|
4608 | =item C<1> - faster/larger code |
|
|
4609 | |
|
|
4610 | Use larger code to speed up some operations. |
|
|
4611 | |
|
|
4612 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4613 | code size by roughly 30% on amd64). |
|
|
4614 | |
|
|
4615 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4616 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4617 | assertions. |
|
|
4618 | |
|
|
4619 | =item C<2> - faster/larger data structures |
|
|
4620 | |
|
|
4621 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4622 | hash table sizes and so on. This will usually further increase code size |
|
|
4623 | and can additionally have an effect on the size of data structures at |
|
|
4624 | runtime. |
|
|
4625 | |
|
|
4626 | =item C<4> - full API configuration |
|
|
4627 | |
|
|
4628 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4629 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4630 | |
|
|
4631 | =item C<8> - full API |
|
|
4632 | |
|
|
4633 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4634 | details on which parts of the API are still available without this |
|
|
4635 | feature, and do not complain if this subset changes over time. |
|
|
4636 | |
|
|
4637 | =item C<16> - enable all optional watcher types |
|
|
4638 | |
|
|
4639 | Enables all optional watcher types. If you want to selectively enable |
|
|
4640 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4641 | embed, async, child...) you can enable them manually by defining |
|
|
4642 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4643 | |
|
|
4644 | =item C<32> - enable all backends |
|
|
4645 | |
|
|
4646 | This enables all backends - without this feature, you need to enable at |
|
|
4647 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4648 | |
|
|
4649 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4650 | |
|
|
4651 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4652 | default. |
|
|
4653 | |
|
|
4654 | =back |
|
|
4655 | |
|
|
4656 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4657 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4658 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4659 | watchers, timers and monotonic clock support. |
|
|
4660 | |
|
|
4661 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4662 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4663 | your program might be left out as well - a binary starting a timer and an |
|
|
4664 | I/O watcher then might come out at only 5Kb. |
|
|
4665 | |
|
|
4666 | =item EV_API_STATIC |
|
|
4667 | |
|
|
4668 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4669 | will have static linkage. This means that libev will not export any |
|
|
4670 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4671 | when you embed libev, only want to use libev functions in a single file, |
|
|
4672 | and do not want its identifiers to be visible. |
|
|
4673 | |
|
|
4674 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4675 | wants to use libev. |
|
|
4676 | |
|
|
4677 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4678 | doesn't support the required declaration syntax. |
|
|
4679 | |
|
|
4680 | =item EV_AVOID_STDIO |
|
|
4681 | |
|
|
4682 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4683 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4684 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4685 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4686 | big. |
|
|
4687 | |
|
|
4688 | Note that error messages might become less precise when this option is |
|
|
4689 | enabled. |
|
|
4690 | |
|
|
4691 | =item EV_NSIG |
|
|
4692 | |
|
|
4693 | The highest supported signal number, +1 (or, the number of |
|
|
4694 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4695 | automatically, but sometimes this fails, in which case it can be |
|
|
4696 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4697 | good for about any system in existence) can save some memory, as libev |
|
|
4698 | statically allocates some 12-24 bytes per signal number. |
2909 | |
4699 | |
2910 | =item EV_PID_HASHSIZE |
4700 | =item EV_PID_HASHSIZE |
2911 | |
4701 | |
2912 | C<ev_child> watchers use a small hash table to distribute workload by |
4702 | C<ev_child> watchers use a small hash table to distribute workload by |
2913 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4703 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
2914 | than enough. If you need to manage thousands of children you might want to |
4704 | usually more than enough. If you need to manage thousands of children you |
2915 | increase this value (I<must> be a power of two). |
4705 | might want to increase this value (I<must> be a power of two). |
2916 | |
4706 | |
2917 | =item EV_INOTIFY_HASHSIZE |
4707 | =item EV_INOTIFY_HASHSIZE |
2918 | |
4708 | |
2919 | C<ev_stat> watchers use a small hash table to distribute workload by |
4709 | C<ev_stat> watchers use a small hash table to distribute workload by |
2920 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4710 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
2921 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4711 | disabled), usually more than enough. If you need to manage thousands of |
2922 | watchers you might want to increase this value (I<must> be a power of |
4712 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
2923 | two). |
4713 | power of two). |
|
|
4714 | |
|
|
4715 | =item EV_USE_4HEAP |
|
|
4716 | |
|
|
4717 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4718 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
4719 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
4720 | faster performance with many (thousands) of watchers. |
|
|
4721 | |
|
|
4722 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4723 | will be C<0>. |
|
|
4724 | |
|
|
4725 | =item EV_HEAP_CACHE_AT |
|
|
4726 | |
|
|
4727 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
4728 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
4729 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
4730 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
4731 | but avoids random read accesses on heap changes. This improves performance |
|
|
4732 | noticeably with many (hundreds) of watchers. |
|
|
4733 | |
|
|
4734 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4735 | will be C<0>. |
|
|
4736 | |
|
|
4737 | =item EV_VERIFY |
|
|
4738 | |
|
|
4739 | Controls how much internal verification (see C<ev_verify ()>) will |
|
|
4740 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
4741 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
4742 | called. If set to C<2>, then the internal verification code will be |
|
|
4743 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
4744 | verification code will be called very frequently, which will slow down |
|
|
4745 | libev considerably. |
|
|
4746 | |
|
|
4747 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
|
|
4748 | will be C<0>. |
2924 | |
4749 | |
2925 | =item EV_COMMON |
4750 | =item EV_COMMON |
2926 | |
4751 | |
2927 | By default, all watchers have a C<void *data> member. By redefining |
4752 | By default, all watchers have a C<void *data> member. By redefining |
2928 | this macro to a something else you can include more and other types of |
4753 | this macro to something else you can include more and other types of |
2929 | members. You have to define it each time you include one of the files, |
4754 | members. You have to define it each time you include one of the files, |
2930 | though, and it must be identical each time. |
4755 | though, and it must be identical each time. |
2931 | |
4756 | |
2932 | For example, the perl EV module uses something like this: |
4757 | For example, the perl EV module uses something like this: |
2933 | |
4758 | |
2934 | #define EV_COMMON \ |
4759 | #define EV_COMMON \ |
2935 | SV *self; /* contains this struct */ \ |
4760 | SV *self; /* contains this struct */ \ |
2936 | SV *cb_sv, *fh /* note no trailing ";" */ |
4761 | SV *cb_sv, *fh /* note no trailing ";" */ |
2937 | |
4762 | |
2938 | =item EV_CB_DECLARE (type) |
4763 | =item EV_CB_DECLARE (type) |
2939 | |
4764 | |
2940 | =item EV_CB_INVOKE (watcher, revents) |
4765 | =item EV_CB_INVOKE (watcher, revents) |
2941 | |
4766 | |
… | |
… | |
2946 | definition and a statement, respectively. See the F<ev.h> header file for |
4771 | definition and a statement, respectively. See the F<ev.h> header file for |
2947 | their default definitions. One possible use for overriding these is to |
4772 | their default definitions. One possible use for overriding these is to |
2948 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4773 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2949 | method calls instead of plain function calls in C++. |
4774 | method calls instead of plain function calls in C++. |
2950 | |
4775 | |
|
|
4776 | =back |
|
|
4777 | |
2951 | =head2 EXPORTED API SYMBOLS |
4778 | =head2 EXPORTED API SYMBOLS |
2952 | |
4779 | |
2953 | If you need to re-export the API (e.g. via a dll) and you need a list of |
4780 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
2954 | exported symbols, you can use the provided F<Symbol.*> files which list |
4781 | exported symbols, you can use the provided F<Symbol.*> files which list |
2955 | all public symbols, one per line: |
4782 | all public symbols, one per line: |
2956 | |
4783 | |
2957 | Symbols.ev for libev proper |
4784 | Symbols.ev for libev proper |
2958 | Symbols.event for the libevent emulation |
4785 | Symbols.event for the libevent emulation |
2959 | |
4786 | |
2960 | This can also be used to rename all public symbols to avoid clashes with |
4787 | This can also be used to rename all public symbols to avoid clashes with |
2961 | multiple versions of libev linked together (which is obviously bad in |
4788 | multiple versions of libev linked together (which is obviously bad in |
2962 | itself, but sometimes it is inconvinient to avoid this). |
4789 | itself, but sometimes it is inconvenient to avoid this). |
2963 | |
4790 | |
2964 | A sed command like this will create wrapper C<#define>'s that you need to |
4791 | A sed command like this will create wrapper C<#define>'s that you need to |
2965 | include before including F<ev.h>: |
4792 | include before including F<ev.h>: |
2966 | |
4793 | |
2967 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
4794 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
… | |
… | |
2984 | file. |
4811 | file. |
2985 | |
4812 | |
2986 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4813 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
2987 | that everybody includes and which overrides some configure choices: |
4814 | that everybody includes and which overrides some configure choices: |
2988 | |
4815 | |
2989 | #define EV_MINIMAL 1 |
4816 | #define EV_FEATURES 8 |
2990 | #define EV_USE_POLL 0 |
4817 | #define EV_USE_SELECT 1 |
2991 | #define EV_MULTIPLICITY 0 |
|
|
2992 | #define EV_PERIODIC_ENABLE 0 |
4818 | #define EV_PREPARE_ENABLE 1 |
|
|
4819 | #define EV_IDLE_ENABLE 1 |
2993 | #define EV_STAT_ENABLE 0 |
4820 | #define EV_SIGNAL_ENABLE 1 |
2994 | #define EV_FORK_ENABLE 0 |
4821 | #define EV_CHILD_ENABLE 1 |
|
|
4822 | #define EV_USE_STDEXCEPT 0 |
2995 | #define EV_CONFIG_H <config.h> |
4823 | #define EV_CONFIG_H <config.h> |
2996 | #define EV_MINPRI 0 |
|
|
2997 | #define EV_MAXPRI 0 |
|
|
2998 | |
4824 | |
2999 | #include "ev++.h" |
4825 | #include "ev++.h" |
3000 | |
4826 | |
3001 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4827 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3002 | |
4828 | |
3003 | #include "ev_cpp.h" |
4829 | #include "ev_cpp.h" |
3004 | #include "ev.c" |
4830 | #include "ev.c" |
3005 | |
4831 | |
|
|
4832 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3006 | |
4833 | |
3007 | =head1 COMPLEXITIES |
4834 | =head2 THREADS AND COROUTINES |
3008 | |
4835 | |
3009 | In this section the complexities of (many of) the algorithms used inside |
4836 | =head3 THREADS |
3010 | libev will be explained. For complexity discussions about backends see the |
|
|
3011 | documentation for C<ev_default_init>. |
|
|
3012 | |
4837 | |
3013 | All of the following are about amortised time: If an array needs to be |
4838 | All libev functions are reentrant and thread-safe unless explicitly |
3014 | extended, libev needs to realloc and move the whole array, but this |
4839 | documented otherwise, but libev implements no locking itself. This means |
3015 | happens asymptotically never with higher number of elements, so O(1) might |
4840 | that you can use as many loops as you want in parallel, as long as there |
3016 | mean it might do a lengthy realloc operation in rare cases, but on average |
4841 | are no concurrent calls into any libev function with the same loop |
3017 | it is much faster and asymptotically approaches constant time. |
4842 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4843 | of course): libev guarantees that different event loops share no data |
|
|
4844 | structures that need any locking. |
|
|
4845 | |
|
|
4846 | Or to put it differently: calls with different loop parameters can be done |
|
|
4847 | concurrently from multiple threads, calls with the same loop parameter |
|
|
4848 | must be done serially (but can be done from different threads, as long as |
|
|
4849 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
4850 | a mutex per loop). |
|
|
4851 | |
|
|
4852 | Specifically to support threads (and signal handlers), libev implements |
|
|
4853 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4854 | concurrency on the same event loop, namely waking it up "from the |
|
|
4855 | outside". |
|
|
4856 | |
|
|
4857 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4858 | without or something else still) is best for your problem, then I cannot |
|
|
4859 | help you, but here is some generic advice: |
3018 | |
4860 | |
3019 | =over 4 |
4861 | =over 4 |
3020 | |
4862 | |
3021 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4863 | =item * most applications have a main thread: use the default libev loop |
|
|
4864 | in that thread, or create a separate thread running only the default loop. |
3022 | |
4865 | |
3023 | This means that, when you have a watcher that triggers in one hour and |
4866 | This helps integrating other libraries or software modules that use libev |
3024 | there are 100 watchers that would trigger before that then inserting will |
4867 | themselves and don't care/know about threading. |
3025 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3026 | |
4868 | |
3027 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4869 | =item * one loop per thread is usually a good model. |
3028 | |
4870 | |
3029 | That means that changing a timer costs less than removing/adding them |
4871 | Doing this is almost never wrong, sometimes a better-performance model |
3030 | as only the relative motion in the event queue has to be paid for. |
4872 | exists, but it is always a good start. |
3031 | |
4873 | |
3032 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4874 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
4875 | loop is handed through multiple threads in a kind of round-robin fashion. |
3033 | |
4876 | |
3034 | These just add the watcher into an array or at the head of a list. |
4877 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
4878 | better than you currently do :-) |
3035 | |
4879 | |
3036 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4880 | =item * often you need to talk to some other thread which blocks in the |
|
|
4881 | event loop. |
3037 | |
4882 | |
3038 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4883 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
4884 | (or from signal contexts...). |
3039 | |
4885 | |
3040 | These watchers are stored in lists then need to be walked to find the |
4886 | An example use would be to communicate signals or other events that only |
3041 | correct watcher to remove. The lists are usually short (you don't usually |
4887 | work in the default loop by registering the signal watcher with the |
3042 | have many watchers waiting for the same fd or signal). |
4888 | default loop and triggering an C<ev_async> watcher from the default loop |
3043 | |
4889 | watcher callback into the event loop interested in the signal. |
3044 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3045 | |
|
|
3046 | By virtue of using a binary heap, the next timer is always found at the |
|
|
3047 | beginning of the storage array. |
|
|
3048 | |
|
|
3049 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3050 | |
|
|
3051 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3052 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3053 | on backend and wether C<ev_io_set> was used). |
|
|
3054 | |
|
|
3055 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3056 | |
|
|
3057 | =item Priority handling: O(number_of_priorities) |
|
|
3058 | |
|
|
3059 | Priorities are implemented by allocating some space for each |
|
|
3060 | priority. When doing priority-based operations, libev usually has to |
|
|
3061 | linearly search all the priorities, but starting/stopping and activating |
|
|
3062 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3063 | |
|
|
3064 | =item Sending an ev_async: O(1) |
|
|
3065 | |
|
|
3066 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3067 | |
|
|
3068 | =item Processing signals: O(max_signal_number) |
|
|
3069 | |
|
|
3070 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3071 | calls in the current loop iteration. Checking for async and signal events |
|
|
3072 | involves iterating over all running async watchers or all signal numbers. |
|
|
3073 | |
4890 | |
3074 | =back |
4891 | =back |
3075 | |
4892 | |
|
|
4893 | See also L<THREAD LOCKING EXAMPLE>. |
3076 | |
4894 | |
3077 | =head1 Win32 platform limitations and workarounds |
4895 | =head3 COROUTINES |
|
|
4896 | |
|
|
4897 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
4898 | libev fully supports nesting calls to its functions from different |
|
|
4899 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
|
|
4900 | different coroutines, and switch freely between both coroutines running |
|
|
4901 | the loop, as long as you don't confuse yourself). The only exception is |
|
|
4902 | that you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
4903 | |
|
|
4904 | Care has been taken to ensure that libev does not keep local state inside |
|
|
4905 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
|
|
4906 | they do not call any callbacks. |
|
|
4907 | |
|
|
4908 | =head2 COMPILER WARNINGS |
|
|
4909 | |
|
|
4910 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4911 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4912 | scared by this. |
|
|
4913 | |
|
|
4914 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
4915 | has different warnings, and each user has different tastes regarding |
|
|
4916 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4917 | targeting a specific compiler and compiler-version. |
|
|
4918 | |
|
|
4919 | Another reason is that some compiler warnings require elaborate |
|
|
4920 | workarounds, or other changes to the code that make it less clear and less |
|
|
4921 | maintainable. |
|
|
4922 | |
|
|
4923 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4924 | wrong (because they don't actually warn about the condition their message |
|
|
4925 | seems to warn about). For example, certain older gcc versions had some |
|
|
4926 | warnings that resulted in an extreme number of false positives. These have |
|
|
4927 | been fixed, but some people still insist on making code warn-free with |
|
|
4928 | such buggy versions. |
|
|
4929 | |
|
|
4930 | While libev is written to generate as few warnings as possible, |
|
|
4931 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4932 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4933 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4934 | warnings, not errors, or proof of bugs. |
|
|
4935 | |
|
|
4936 | |
|
|
4937 | =head2 VALGRIND |
|
|
4938 | |
|
|
4939 | Valgrind has a special section here because it is a popular tool that is |
|
|
4940 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
4941 | |
|
|
4942 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4943 | in libev, then check twice: If valgrind reports something like: |
|
|
4944 | |
|
|
4945 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4946 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4947 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
4948 | |
|
|
4949 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4950 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
4951 | |
|
|
4952 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4953 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4954 | although an acceptable workaround has been found here), or it might be |
|
|
4955 | confused. |
|
|
4956 | |
|
|
4957 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
4958 | make it into some kind of religion. |
|
|
4959 | |
|
|
4960 | If you are unsure about something, feel free to contact the mailing list |
|
|
4961 | with the full valgrind report and an explanation on why you think this |
|
|
4962 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4963 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4964 | of learning how to interpret valgrind properly. |
|
|
4965 | |
|
|
4966 | If you need, for some reason, empty reports from valgrind for your project |
|
|
4967 | I suggest using suppression lists. |
|
|
4968 | |
|
|
4969 | |
|
|
4970 | =head1 PORTABILITY NOTES |
|
|
4971 | |
|
|
4972 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4973 | |
|
|
4974 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4975 | interfaces but I<disables> them by default. |
|
|
4976 | |
|
|
4977 | That means that libev compiled in the default environment doesn't support |
|
|
4978 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4979 | |
|
|
4980 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4981 | by enabling the large file API, which makes them incompatible with the |
|
|
4982 | standard libev compiled for their system. |
|
|
4983 | |
|
|
4984 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4985 | suddenly make it incompatible to the default compile time environment, |
|
|
4986 | i.e. all programs not using special compile switches. |
|
|
4987 | |
|
|
4988 | =head2 OS/X AND DARWIN BUGS |
|
|
4989 | |
|
|
4990 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4991 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4992 | OpenGL drivers. |
|
|
4993 | |
|
|
4994 | =head3 C<kqueue> is buggy |
|
|
4995 | |
|
|
4996 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4997 | only sockets, many support pipes. |
|
|
4998 | |
|
|
4999 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5000 | rotten platform, but of course you can still ask for it when creating a |
|
|
5001 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5002 | probably going to work well. |
|
|
5003 | |
|
|
5004 | =head3 C<poll> is buggy |
|
|
5005 | |
|
|
5006 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5007 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5008 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5009 | |
|
|
5010 | Libev tries to work around this by not using C<poll> by default on |
|
|
5011 | this rotten platform, but of course you can still ask for it when creating |
|
|
5012 | a loop. |
|
|
5013 | |
|
|
5014 | =head3 C<select> is buggy |
|
|
5015 | |
|
|
5016 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5017 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5018 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5019 | you use more. |
|
|
5020 | |
|
|
5021 | There is an undocumented "workaround" for this - defining |
|
|
5022 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5023 | work on OS/X. |
|
|
5024 | |
|
|
5025 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5026 | |
|
|
5027 | =head3 C<errno> reentrancy |
|
|
5028 | |
|
|
5029 | The default compile environment on Solaris is unfortunately so |
|
|
5030 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5031 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5032 | defined by default. A valid, if stupid, implementation choice. |
|
|
5033 | |
|
|
5034 | If you want to use libev in threaded environments you have to make sure |
|
|
5035 | it's compiled with C<_REENTRANT> defined. |
|
|
5036 | |
|
|
5037 | =head3 Event port backend |
|
|
5038 | |
|
|
5039 | The scalable event interface for Solaris is called "event |
|
|
5040 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5041 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5042 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5043 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5044 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5045 | great. |
|
|
5046 | |
|
|
5047 | If you can't get it to work, you can try running the program by setting |
|
|
5048 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5049 | C<select> backends. |
|
|
5050 | |
|
|
5051 | =head2 AIX POLL BUG |
|
|
5052 | |
|
|
5053 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5054 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5055 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5056 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5057 | |
|
|
5058 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5059 | |
|
|
5060 | =head3 General issues |
3078 | |
5061 | |
3079 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5062 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3080 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5063 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3081 | model. Libev still offers limited functionality on this platform in |
5064 | model. Libev still offers limited functionality on this platform in |
3082 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5065 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3083 | descriptors. This only applies when using Win32 natively, not when using |
5066 | descriptors. This only applies when using Win32 natively, not when using |
3084 | e.g. cygwin. |
5067 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5068 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5069 | environment. |
|
|
5070 | |
|
|
5071 | Lifting these limitations would basically require the full |
|
|
5072 | re-implementation of the I/O system. If you are into this kind of thing, |
|
|
5073 | then note that glib does exactly that for you in a very portable way (note |
|
|
5074 | also that glib is the slowest event library known to man). |
3085 | |
5075 | |
3086 | There is no supported compilation method available on windows except |
5076 | There is no supported compilation method available on windows except |
3087 | embedding it into other applications. |
5077 | embedding it into other applications. |
3088 | |
5078 | |
|
|
5079 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
5080 | tries its best, but under most conditions, signals will simply not work. |
|
|
5081 | |
|
|
5082 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
5083 | accept large writes: instead of resulting in a partial write, windows will |
|
|
5084 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
5085 | so make sure you only write small amounts into your sockets (less than a |
|
|
5086 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
5087 | available). |
|
|
5088 | |
3089 | Due to the many, low, and arbitrary limits on the win32 platform and the |
5089 | Due to the many, low, and arbitrary limits on the win32 platform and |
3090 | abysmal performance of winsockets, using a large number of sockets is not |
5090 | the abysmal performance of winsockets, using a large number of sockets |
3091 | recommended (and not reasonable). If your program needs to use more than |
5091 | is not recommended (and not reasonable). If your program needs to use |
3092 | a hundred or so sockets, then likely it needs to use a totally different |
5092 | more than a hundred or so sockets, then likely it needs to use a totally |
3093 | implementation for windows, as libev offers the POSIX model, which cannot |
5093 | different implementation for windows, as libev offers the POSIX readiness |
3094 | be implemented efficiently on windows (microsoft monopoly games). |
5094 | notification model, which cannot be implemented efficiently on windows |
|
|
5095 | (due to Microsoft monopoly games). |
3095 | |
5096 | |
3096 | =over 4 |
5097 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
5098 | section for details) and use the following F<evwrap.h> header file instead |
|
|
5099 | of F<ev.h>: |
3097 | |
5100 | |
|
|
5101 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
5102 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
5103 | |
|
|
5104 | #include "ev.h" |
|
|
5105 | |
|
|
5106 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
5107 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
5108 | |
|
|
5109 | #include "evwrap.h" |
|
|
5110 | #include "ev.c" |
|
|
5111 | |
3098 | =item The winsocket select function |
5112 | =head3 The winsocket C<select> function |
3099 | |
5113 | |
3100 | The winsocket C<select> function doesn't follow POSIX in that it requires |
5114 | The winsocket C<select> function doesn't follow POSIX in that it |
3101 | socket I<handles> and not socket I<file descriptors>. This makes select |
5115 | requires socket I<handles> and not socket I<file descriptors> (it is |
3102 | very inefficient, and also requires a mapping from file descriptors |
5116 | also extremely buggy). This makes select very inefficient, and also |
3103 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
5117 | requires a mapping from file descriptors to socket handles (the Microsoft |
3104 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
5118 | C runtime provides the function C<_open_osfhandle> for this). See the |
3105 | symbols for more info. |
5119 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
5120 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
3106 | |
5121 | |
3107 | The configuration for a "naked" win32 using the microsoft runtime |
5122 | The configuration for a "naked" win32 using the Microsoft runtime |
3108 | libraries and raw winsocket select is: |
5123 | libraries and raw winsocket select is: |
3109 | |
5124 | |
3110 | #define EV_USE_SELECT 1 |
5125 | #define EV_USE_SELECT 1 |
3111 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5126 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3112 | |
5127 | |
3113 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5128 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3114 | complexity in the O(n²) range when using win32. |
5129 | complexity in the O(n²) range when using win32. |
3115 | |
5130 | |
3116 | =item Limited number of file descriptors |
5131 | =head3 Limited number of file descriptors |
3117 | |
5132 | |
3118 | Windows has numerous arbitrary (and low) limits on things. Early versions |
5133 | Windows has numerous arbitrary (and low) limits on things. |
3119 | of winsocket's select only supported waiting for a max. of C<64> handles |
5134 | |
|
|
5135 | Early versions of winsocket's select only supported waiting for a maximum |
3120 | (probably owning to the fact that all windows kernels can only wait for |
5136 | of C<64> handles (probably owning to the fact that all windows kernels |
3121 | C<64> things at the same time internally; microsoft recommends spawning a |
5137 | can only wait for C<64> things at the same time internally; Microsoft |
3122 | chain of threads and wait for 63 handles and the previous thread in each). |
5138 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
5139 | previous thread in each. Sounds great!). |
3123 | |
5140 | |
3124 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
5141 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3125 | to some high number (e.g. C<2048>) before compiling the winsocket select |
5142 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3126 | call (which might be in libev or elsewhere, for example, perl does its own |
5143 | call (which might be in libev or elsewhere, for example, perl and many |
3127 | select emulation on windows). |
5144 | other interpreters do their own select emulation on windows). |
3128 | |
5145 | |
3129 | Another limit is the number of file descriptors in the microsoft runtime |
5146 | Another limit is the number of file descriptors in the Microsoft runtime |
3130 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
5147 | libraries, which by default is C<64> (there must be a hidden I<64> |
3131 | or something like this inside microsoft). You can increase this by calling |
5148 | fetish or something like this inside Microsoft). You can increase this |
3132 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
5149 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3133 | arbitrary limit), but is broken in many versions of the microsoft runtime |
5150 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3134 | libraries. |
|
|
3135 | |
|
|
3136 | This might get you to about C<512> or C<2048> sockets (depending on |
5151 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3137 | windows version and/or the phase of the moon). To get more, you need to |
5152 | (depending on windows version and/or the phase of the moon). To get more, |
3138 | wrap all I/O functions and provide your own fd management, but the cost of |
5153 | you need to wrap all I/O functions and provide your own fd management, but |
3139 | calling select (O(n²)) will likely make this unworkable. |
5154 | the cost of calling select (O(n²)) will likely make this unworkable. |
|
|
5155 | |
|
|
5156 | =head2 PORTABILITY REQUIREMENTS |
|
|
5157 | |
|
|
5158 | In addition to a working ISO-C implementation and of course the |
|
|
5159 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
5160 | |
|
|
5161 | =over 4 |
|
|
5162 | |
|
|
5163 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
5164 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
5165 | |
|
|
5166 | Libev assumes not only that all watcher pointers have the same internal |
|
|
5167 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
5168 | assumes that the same (machine) code can be used to call any watcher |
|
|
5169 | callback: The watcher callbacks have different type signatures, but libev |
|
|
5170 | calls them using an C<ev_watcher *> internally. |
|
|
5171 | |
|
|
5172 | =item pointer accesses must be thread-atomic |
|
|
5173 | |
|
|
5174 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5175 | writable in one piece - this is the case on all current architectures. |
|
|
5176 | |
|
|
5177 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
5178 | |
|
|
5179 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
5180 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
5181 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
5182 | believed to be sufficiently portable. |
|
|
5183 | |
|
|
5184 | =item C<sigprocmask> must work in a threaded environment |
|
|
5185 | |
|
|
5186 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
5187 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
5188 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
5189 | thread" or will block signals process-wide, both behaviours would |
|
|
5190 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
5191 | C<pthread_sigmask> could complicate things, however. |
|
|
5192 | |
|
|
5193 | The most portable way to handle signals is to block signals in all threads |
|
|
5194 | except the initial one, and run the default loop in the initial thread as |
|
|
5195 | well. |
|
|
5196 | |
|
|
5197 | =item C<long> must be large enough for common memory allocation sizes |
|
|
5198 | |
|
|
5199 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
5200 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
5201 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
5202 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
5203 | watchers. |
|
|
5204 | |
|
|
5205 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
5206 | |
|
|
5207 | The type C<double> is used to represent timestamps. It is required to |
|
|
5208 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
|
|
5209 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5210 | (the design goal for libev). This requirement is overfulfilled by |
|
|
5211 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5212 | |
|
|
5213 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5214 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5215 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5216 | something like that, just kidding). |
3140 | |
5217 | |
3141 | =back |
5218 | =back |
3142 | |
5219 | |
|
|
5220 | If you know of other additional requirements drop me a note. |
|
|
5221 | |
|
|
5222 | |
|
|
5223 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
5224 | |
|
|
5225 | In this section the complexities of (many of) the algorithms used inside |
|
|
5226 | libev will be documented. For complexity discussions about backends see |
|
|
5227 | the documentation for C<ev_default_init>. |
|
|
5228 | |
|
|
5229 | All of the following are about amortised time: If an array needs to be |
|
|
5230 | extended, libev needs to realloc and move the whole array, but this |
|
|
5231 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
5232 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
5233 | average it is much faster and asymptotically approaches constant time. |
|
|
5234 | |
|
|
5235 | =over 4 |
|
|
5236 | |
|
|
5237 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
5238 | |
|
|
5239 | This means that, when you have a watcher that triggers in one hour and |
|
|
5240 | there are 100 watchers that would trigger before that, then inserting will |
|
|
5241 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
5242 | |
|
|
5243 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
5244 | |
|
|
5245 | That means that changing a timer costs less than removing/adding them, |
|
|
5246 | as only the relative motion in the event queue has to be paid for. |
|
|
5247 | |
|
|
5248 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
5249 | |
|
|
5250 | These just add the watcher into an array or at the head of a list. |
|
|
5251 | |
|
|
5252 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
5253 | |
|
|
5254 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
5255 | |
|
|
5256 | These watchers are stored in lists, so they need to be walked to find the |
|
|
5257 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
5258 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
5259 | is rare). |
|
|
5260 | |
|
|
5261 | =item Finding the next timer in each loop iteration: O(1) |
|
|
5262 | |
|
|
5263 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
5264 | fixed position in the storage array. |
|
|
5265 | |
|
|
5266 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
5267 | |
|
|
5268 | A change means an I/O watcher gets started or stopped, which requires |
|
|
5269 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
5270 | on backend and whether C<ev_io_set> was used). |
|
|
5271 | |
|
|
5272 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
5273 | |
|
|
5274 | =item Priority handling: O(number_of_priorities) |
|
|
5275 | |
|
|
5276 | Priorities are implemented by allocating some space for each |
|
|
5277 | priority. When doing priority-based operations, libev usually has to |
|
|
5278 | linearly search all the priorities, but starting/stopping and activating |
|
|
5279 | watchers becomes O(1) with respect to priority handling. |
|
|
5280 | |
|
|
5281 | =item Sending an ev_async: O(1) |
|
|
5282 | |
|
|
5283 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
5284 | |
|
|
5285 | =item Processing signals: O(max_signal_number) |
|
|
5286 | |
|
|
5287 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
5288 | calls in the current loop iteration and the loop is currently |
|
|
5289 | blocked. Checking for async and signal events involves iterating over all |
|
|
5290 | running async watchers or all signal numbers. |
|
|
5291 | |
|
|
5292 | =back |
|
|
5293 | |
|
|
5294 | |
|
|
5295 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5296 | |
|
|
5297 | The major version 4 introduced some incompatible changes to the API. |
|
|
5298 | |
|
|
5299 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5300 | for all changes, so most programs should still compile. The compatibility |
|
|
5301 | layer might be removed in later versions of libev, so better update to the |
|
|
5302 | new API early than late. |
|
|
5303 | |
|
|
5304 | =over 4 |
|
|
5305 | |
|
|
5306 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5307 | |
|
|
5308 | The backward compatibility mechanism can be controlled by |
|
|
5309 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5310 | section. |
|
|
5311 | |
|
|
5312 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5313 | |
|
|
5314 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5315 | |
|
|
5316 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5317 | ev_loop_fork (EV_DEFAULT); |
|
|
5318 | |
|
|
5319 | =item function/symbol renames |
|
|
5320 | |
|
|
5321 | A number of functions and symbols have been renamed: |
|
|
5322 | |
|
|
5323 | ev_loop => ev_run |
|
|
5324 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5325 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5326 | |
|
|
5327 | ev_unloop => ev_break |
|
|
5328 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5329 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5330 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5331 | |
|
|
5332 | EV_TIMEOUT => EV_TIMER |
|
|
5333 | |
|
|
5334 | ev_loop_count => ev_iteration |
|
|
5335 | ev_loop_depth => ev_depth |
|
|
5336 | ev_loop_verify => ev_verify |
|
|
5337 | |
|
|
5338 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5339 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5340 | associated constants have been renamed to not collide with the C<struct |
|
|
5341 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5342 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5343 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5344 | typedef. |
|
|
5345 | |
|
|
5346 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5347 | |
|
|
5348 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5349 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5350 | and work, but the library code will of course be larger. |
|
|
5351 | |
|
|
5352 | =back |
|
|
5353 | |
|
|
5354 | |
|
|
5355 | =head1 GLOSSARY |
|
|
5356 | |
|
|
5357 | =over 4 |
|
|
5358 | |
|
|
5359 | =item active |
|
|
5360 | |
|
|
5361 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5362 | See L<WATCHER STATES> for details. |
|
|
5363 | |
|
|
5364 | =item application |
|
|
5365 | |
|
|
5366 | In this document, an application is whatever is using libev. |
|
|
5367 | |
|
|
5368 | =item backend |
|
|
5369 | |
|
|
5370 | The part of the code dealing with the operating system interfaces. |
|
|
5371 | |
|
|
5372 | =item callback |
|
|
5373 | |
|
|
5374 | The address of a function that is called when some event has been |
|
|
5375 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5376 | received the event, and the actual event bitset. |
|
|
5377 | |
|
|
5378 | =item callback/watcher invocation |
|
|
5379 | |
|
|
5380 | The act of calling the callback associated with a watcher. |
|
|
5381 | |
|
|
5382 | =item event |
|
|
5383 | |
|
|
5384 | A change of state of some external event, such as data now being available |
|
|
5385 | for reading on a file descriptor, time having passed or simply not having |
|
|
5386 | any other events happening anymore. |
|
|
5387 | |
|
|
5388 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5389 | C<EV_TIMER>). |
|
|
5390 | |
|
|
5391 | =item event library |
|
|
5392 | |
|
|
5393 | A software package implementing an event model and loop. |
|
|
5394 | |
|
|
5395 | =item event loop |
|
|
5396 | |
|
|
5397 | An entity that handles and processes external events and converts them |
|
|
5398 | into callback invocations. |
|
|
5399 | |
|
|
5400 | =item event model |
|
|
5401 | |
|
|
5402 | The model used to describe how an event loop handles and processes |
|
|
5403 | watchers and events. |
|
|
5404 | |
|
|
5405 | =item pending |
|
|
5406 | |
|
|
5407 | A watcher is pending as soon as the corresponding event has been |
|
|
5408 | detected. See L<WATCHER STATES> for details. |
|
|
5409 | |
|
|
5410 | =item real time |
|
|
5411 | |
|
|
5412 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5413 | |
|
|
5414 | =item wall-clock time |
|
|
5415 | |
|
|
5416 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5417 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5418 | clock. |
|
|
5419 | |
|
|
5420 | =item watcher |
|
|
5421 | |
|
|
5422 | A data structure that describes interest in certain events. Watchers need |
|
|
5423 | to be started (attached to an event loop) before they can receive events. |
|
|
5424 | |
|
|
5425 | =back |
3143 | |
5426 | |
3144 | =head1 AUTHOR |
5427 | =head1 AUTHOR |
3145 | |
5428 | |
3146 | Marc Lehmann <libev@schmorp.de>. |
5429 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5430 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
3147 | |
5431 | |