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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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8 | |
10 | |
9 | =head2 EXAMPLE PROGRAM |
11 | =head2 EXAMPLE PROGRAM |
10 | |
12 | |
11 | // a single header file is required |
13 | // a single header file is required |
12 | #include <ev.h> |
14 | #include <ev.h> |
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15 | |
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16 | #include <stdio.h> // for puts |
13 | |
17 | |
14 | // every watcher type has its own typedef'd struct |
18 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
19 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
20 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
21 | ev_timer timeout_watcher; |
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24 | puts ("stdin ready"); |
28 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
29 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
30 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
31 | ev_io_stop (EV_A_ w); |
28 | |
32 | |
29 | // this causes all nested ev_loop's to stop iterating |
33 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
34 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
35 | } |
32 | |
36 | |
33 | // another callback, this time for a time-out |
37 | // another callback, this time for a time-out |
34 | static void |
38 | static void |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
39 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
40 | { |
37 | puts ("timeout"); |
41 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
42 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
43 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
44 | } |
41 | |
45 | |
42 | int |
46 | int |
43 | main (void) |
47 | main (void) |
44 | { |
48 | { |
45 | // use the default event loop unless you have special needs |
49 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
50 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
51 | |
48 | // initialise an io watcher, then start it |
52 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
53 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
54 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
55 | ev_io_start (loop, &stdin_watcher); |
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54 | // simple non-repeating 5.5 second timeout |
58 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
59 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
57 | |
61 | |
58 | // now wait for events to arrive |
62 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
63 | ev_run (loop, 0); |
60 | |
64 | |
61 | // unloop was called, so exit |
65 | // break was called, so exit |
62 | return 0; |
66 | return 0; |
63 | } |
67 | } |
64 | |
68 | |
65 | =head1 DESCRIPTION |
69 | =head1 ABOUT THIS DOCUMENT |
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70 | |
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71 | This document documents the libev software package. |
66 | |
72 | |
67 | The newest version of this document is also available as an html-formatted |
73 | 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 |
74 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
75 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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76 | |
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77 | While this document tries to be as complete as possible in documenting |
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78 | libev, its usage and the rationale behind its design, it is not a tutorial |
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79 | on event-based programming, nor will it introduce event-based programming |
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80 | with libev. |
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81 | |
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82 | Familiarity with event based programming techniques in general is assumed |
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83 | throughout this document. |
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84 | |
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85 | =head1 WHAT TO READ WHEN IN A HURRY |
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86 | |
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87 | This manual tries to be very detailed, but unfortunately, this also makes |
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88 | it very long. If you just want to know the basics of libev, I suggest |
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89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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91 | C<ev_timer> sections in L</WATCHER TYPES>. |
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92 | |
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93 | =head1 ABOUT LIBEV |
70 | |
94 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
97 | these event sources and provide your program with events. |
74 | |
98 | |
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81 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
82 | watcher. |
106 | watcher. |
83 | |
107 | |
84 | =head2 FEATURES |
108 | =head2 FEATURES |
85 | |
109 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
114 | 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 |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
116 | (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 |
117 | 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 |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
119 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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120 | limited support for fork events (C<ev_fork>). |
96 | |
121 | |
97 | It also is quite fast (see this |
122 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
123 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
124 | for example). |
100 | |
125 | |
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103 | Libev is very configurable. In this manual the default (and most common) |
128 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
129 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
130 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
131 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
132 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
133 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
134 | this argument. |
110 | |
135 | |
111 | =head2 TIME REPRESENTATION |
136 | =head2 TIME REPRESENTATION |
112 | |
137 | |
113 | Libev represents time as a single floating point number, representing the |
138 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
139 | 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 |
140 | 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 |
141 | 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 |
142 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
143 | any calculations on it, you should treat it as some floating point value. |
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144 | |
119 | component C<stamp> might indicate, it is also used for time differences |
145 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
146 | time differences (e.g. delays) throughout libev. |
121 | |
147 | |
122 | =head1 ERROR HANDLING |
148 | =head1 ERROR HANDLING |
123 | |
149 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
150 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
151 | and internal errors (bugs). |
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149 | |
175 | |
150 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
151 | |
177 | |
152 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
180 | you actually want to know. Also interesting is the combination of |
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181 | C<ev_now_update> and C<ev_now>. |
155 | |
182 | |
156 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
157 | |
184 | |
158 | Sleep for the given interval: The current thread will be blocked until |
185 | Sleep for the given interval: The current thread will be blocked |
159 | either it is interrupted or the given time interval has passed. Basically |
186 | until either it is interrupted or the given time interval has |
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187 | passed (approximately - it might return a bit earlier even if not |
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188 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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189 | |
160 | this is a sub-second-resolution C<sleep ()>. |
190 | Basically this is a sub-second-resolution C<sleep ()>. |
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191 | |
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192 | The range of the C<interval> is limited - libev only guarantees to work |
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193 | with sleep times of up to one day (C<< interval <= 86400 >>). |
161 | |
194 | |
162 | =item int ev_version_major () |
195 | =item int ev_version_major () |
163 | |
196 | |
164 | =item int ev_version_minor () |
197 | =item int ev_version_minor () |
165 | |
198 | |
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176 | as this indicates an incompatible change. Minor versions are usually |
209 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
210 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
211 | not a problem. |
179 | |
212 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
213 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
214 | version (note, however, that this will not detect other ABI mismatches, |
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215 | such as LFS or reentrancy). |
182 | |
216 | |
183 | assert (("libev version mismatch", |
217 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
218 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
219 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
220 | |
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197 | assert (("sorry, no epoll, no sex", |
231 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
232 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
233 | |
200 | =item unsigned int ev_recommended_backends () |
234 | =item unsigned int ev_recommended_backends () |
201 | |
235 | |
202 | Return the set of all backends compiled into this binary of libev and also |
236 | Return the set of all backends compiled into this binary of libev and |
203 | recommended for this platform. This set is often smaller than the one |
237 | also recommended for this platform, meaning it will work for most file |
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238 | descriptor types. This set is often smaller than the one returned by |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
239 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
240 | and will not be auto-detected unless you explicitly request it (assuming |
206 | (assuming you know what you are doing). This is the set of backends that |
241 | you know what you are doing). This is the set of backends that libev will |
207 | libev will probe for if you specify no backends explicitly. |
242 | probe for if you specify no backends explicitly. |
208 | |
243 | |
209 | =item unsigned int ev_embeddable_backends () |
244 | =item unsigned int ev_embeddable_backends () |
210 | |
245 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
246 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
247 | value is platform-specific but can include backends not available on the |
213 | might be supported on the current system, you would need to look at |
248 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
251 | |
217 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
218 | |
253 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
220 | |
255 | |
221 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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230 | |
265 | |
231 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
232 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
233 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
234 | |
269 | |
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270 | Example: The following is the C<realloc> function that libev itself uses |
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271 | which should work with C<realloc> and C<free> functions of all kinds and |
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272 | is probably a good basis for your own implementation. |
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273 | |
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274 | static void * |
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275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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276 | { |
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277 | if (size) |
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278 | return realloc (ptr, size); |
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279 | |
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280 | free (ptr); |
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281 | return 0; |
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282 | } |
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283 | |
235 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
236 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
237 | |
286 | |
238 | static void * |
287 | static void * |
239 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
240 | { |
289 | { |
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290 | if (!size) |
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291 | { |
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292 | free (ptr); |
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293 | return 0; |
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294 | } |
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295 | |
241 | for (;;) |
296 | for (;;) |
242 | { |
297 | { |
243 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
244 | |
299 | |
245 | if (newptr) |
300 | if (newptr) |
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250 | } |
305 | } |
251 | |
306 | |
252 | ... |
307 | ... |
253 | ev_set_allocator (persistent_realloc); |
308 | ev_set_allocator (persistent_realloc); |
254 | |
309 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
310 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
256 | |
311 | |
257 | Set the callback function to call on a retryable system call error (such |
312 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
313 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
314 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
315 | callback is set, then libev will expect it to remedy the situation, no |
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272 | } |
327 | } |
273 | |
328 | |
274 | ... |
329 | ... |
275 | ev_set_syserr_cb (fatal_error); |
330 | ev_set_syserr_cb (fatal_error); |
276 | |
331 | |
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332 | =item ev_feed_signal (int signum) |
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333 | |
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334 | This function can be used to "simulate" a signal receive. It is completely |
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335 | safe to call this function at any time, from any context, including signal |
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336 | handlers or random threads. |
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337 | |
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338 | Its main use is to customise signal handling in your process, especially |
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339 | in the presence of threads. For example, you could block signals |
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340 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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341 | creating any loops), and in one thread, use C<sigwait> or any other |
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342 | mechanism to wait for signals, then "deliver" them to libev by calling |
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343 | C<ev_feed_signal>. |
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344 | |
277 | =back |
345 | =back |
278 | |
346 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
347 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
348 | |
281 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
349 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
282 | is I<not> optional in this case, as there is also an C<ev_loop> |
350 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | I<function>). |
351 | libev 3 had an C<ev_loop> function colliding with the struct name). |
284 | |
352 | |
285 | The library knows two types of such loops, the I<default> loop, which |
353 | The library knows two types of such loops, the I<default> loop, which |
286 | supports signals and child events, and dynamically created loops which do |
354 | supports child process events, and dynamically created event loops which |
287 | not. |
355 | do not. |
288 | |
356 | |
289 | =over 4 |
357 | =over 4 |
290 | |
358 | |
291 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
359 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
292 | |
360 | |
293 | This will initialise the default event loop if it hasn't been initialised |
361 | This returns the "default" event loop object, which is what you should |
294 | yet and return it. If the default loop could not be initialised, returns |
362 | normally use when you just need "the event loop". Event loop objects and |
295 | false. If it already was initialised it simply returns it (and ignores the |
363 | the C<flags> parameter are described in more detail in the entry for |
296 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
364 | C<ev_loop_new>. |
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365 | |
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366 | If the default loop is already initialised then this function simply |
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367 | returns it (and ignores the flags. If that is troubling you, check |
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368 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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369 | flags, which should almost always be C<0>, unless the caller is also the |
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370 | one calling C<ev_run> or otherwise qualifies as "the main program". |
297 | |
371 | |
298 | If you don't know what event loop to use, use the one returned from this |
372 | If you don't know what event loop to use, use the one returned from this |
299 | function. |
373 | function (or via the C<EV_DEFAULT> macro). |
300 | |
374 | |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
375 | Note that this function is I<not> thread-safe, so if you want to use it |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
376 | from multiple threads, you have to employ some kind of mutex (note also |
303 | as loops cannot be shared easily between threads anyway). |
377 | that this case is unlikely, as loops cannot be shared easily between |
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378 | threads anyway). |
304 | |
379 | |
305 | The default loop is the only loop that can handle C<ev_signal> and |
380 | The default loop is the only loop that can handle C<ev_child> watchers, |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
381 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
382 | a problem for your application you can either create a dynamic loop with |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
383 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
309 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
384 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
310 | C<ev_default_init>. |
385 | |
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386 | Example: This is the most typical usage. |
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387 | |
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388 | if (!ev_default_loop (0)) |
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389 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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390 | |
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391 | Example: Restrict libev to the select and poll backends, and do not allow |
|
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392 | environment settings to be taken into account: |
|
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393 | |
|
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394 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
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395 | |
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396 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
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397 | |
|
|
398 | This will create and initialise a new event loop object. If the loop |
|
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399 | could not be initialised, returns false. |
|
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400 | |
|
|
401 | This function is thread-safe, and one common way to use libev with |
|
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402 | threads is indeed to create one loop per thread, and using the default |
|
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403 | loop in the "main" or "initial" thread. |
311 | |
404 | |
312 | The flags argument can be used to specify special behaviour or specific |
405 | The flags argument can be used to specify special behaviour or specific |
313 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
406 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
314 | |
407 | |
315 | The following flags are supported: |
408 | The following flags are supported: |
… | |
… | |
325 | |
418 | |
326 | If this flag bit is or'ed into the flag value (or the program runs setuid |
419 | If this flag bit is or'ed into the flag value (or the program runs setuid |
327 | or setgid) then libev will I<not> look at the environment variable |
420 | or setgid) then libev will I<not> look at the environment variable |
328 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
421 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
329 | override the flags completely if it is found in the environment. This is |
422 | override the flags completely if it is found in the environment. This is |
330 | useful to try out specific backends to test their performance, or to work |
423 | useful to try out specific backends to test their performance, to work |
331 | around bugs. |
424 | around bugs, or to make libev threadsafe (accessing environment variables |
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425 | cannot be done in a threadsafe way, but usually it works if no other |
|
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426 | thread modifies them). |
332 | |
427 | |
333 | =item C<EVFLAG_FORKCHECK> |
428 | =item C<EVFLAG_FORKCHECK> |
334 | |
429 | |
335 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
430 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
336 | a fork, you can also make libev check for a fork in each iteration by |
431 | make libev check for a fork in each iteration by enabling this flag. |
337 | enabling this flag. |
|
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338 | |
432 | |
339 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
340 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
341 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
342 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
343 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
344 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
345 | |
440 | |
346 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
347 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
348 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
349 | |
444 | |
350 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
351 | environment variable. |
446 | environment variable. |
|
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447 | |
|
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448 | =item C<EVFLAG_NOINOTIFY> |
|
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449 | |
|
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450 | When this flag is specified, then libev will not attempt to use the |
|
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451 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
|
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452 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
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453 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
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454 | |
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455 | =item C<EVFLAG_SIGNALFD> |
|
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456 | |
|
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457 | When this flag is specified, then libev will attempt to use the |
|
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458 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
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459 | delivers signals synchronously, which makes it both faster and might make |
|
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460 | it possible to get the queued signal data. It can also simplify signal |
|
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461 | handling with threads, as long as you properly block signals in your |
|
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462 | threads that are not interested in handling them. |
|
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463 | |
|
|
464 | Signalfd will not be used by default as this changes your signal mask, and |
|
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465 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
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466 | example) that can't properly initialise their signal masks. |
|
|
467 | |
|
|
468 | =item C<EVFLAG_NOSIGMASK> |
|
|
469 | |
|
|
470 | When this flag is specified, then libev will avoid to modify the signal |
|
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471 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
472 | when you want to receive them. |
|
|
473 | |
|
|
474 | This behaviour is useful when you want to do your own signal handling, or |
|
|
475 | want to handle signals only in specific threads and want to avoid libev |
|
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476 | unblocking the signals. |
|
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477 | |
|
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478 | It's also required by POSIX in a threaded program, as libev calls |
|
|
479 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
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480 | |
|
|
481 | This flag's behaviour will become the default in future versions of libev. |
352 | |
482 | |
353 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
483 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
354 | |
484 | |
355 | This is your standard select(2) backend. Not I<completely> standard, as |
485 | This is your standard select(2) backend. Not I<completely> standard, as |
356 | libev tries to roll its own fd_set with no limits on the number of fds, |
486 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
381 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
382 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
383 | |
513 | |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
385 | |
515 | |
|
|
516 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
517 | kernels). |
|
|
518 | |
386 | For few fds, this backend is a bit little slower than poll and select, |
519 | For few fds, this backend is a bit little slower than poll and select, but |
387 | but it scales phenomenally better. While poll and select usually scale |
520 | it scales phenomenally better. While poll and select usually scale like |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
521 | O(total_fds) where total_fds is the total number of fds (or the highest |
389 | epoll scales either O(1) or O(active_fds). |
522 | fd), epoll scales either O(1) or O(active_fds). |
390 | |
523 | |
391 | The epoll mechanism deserves honorable mention as the most misdesigned |
524 | The epoll mechanism deserves honorable mention as the most misdesigned |
392 | of the more advanced event mechanisms: mere annoyances include silently |
525 | of the more advanced event mechanisms: mere annoyances include silently |
393 | dropping file descriptors, requiring a system call per change per file |
526 | dropping file descriptors, requiring a system call per change per file |
394 | descriptor (and unnecessary guessing of parameters), problems with dup and |
527 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
528 | returning before the timeout value, resulting in additional iterations |
|
|
529 | (and only giving 5ms accuracy while select on the same platform gives |
395 | so on. The biggest issue is fork races, however - if a program forks then |
530 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
396 | I<both> parent and child process have to recreate the epoll set, which can |
531 | forks then I<both> parent and child process have to recreate the epoll |
397 | take considerable time (one syscall per file descriptor) and is of course |
532 | set, which can take considerable time (one syscall per file descriptor) |
398 | hard to detect. |
533 | and is of course hard to detect. |
399 | |
534 | |
400 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
535 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
401 | of course I<doesn't>, and epoll just loves to report events for totally |
536 | but of course I<doesn't>, and epoll just loves to report events for |
402 | I<different> file descriptors (even already closed ones, so one cannot |
537 | totally I<different> file descriptors (even already closed ones, so |
403 | even remove them from the set) than registered in the set (especially |
538 | one cannot even remove them from the set) than registered in the set |
404 | on SMP systems). Libev tries to counter these spurious notifications by |
539 | (especially on SMP systems). Libev tries to counter these spurious |
405 | employing an additional generation counter and comparing that against the |
540 | notifications by employing an additional generation counter and comparing |
406 | events to filter out spurious ones, recreating the set when required. |
541 | that against the events to filter out spurious ones, recreating the set |
|
|
542 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
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543 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
544 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
545 | not least, it also refuses to work with some file descriptors which work |
|
|
546 | perfectly fine with C<select> (files, many character devices...). |
|
|
547 | |
|
|
548 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
549 | cobbled together in a hurry, no thought to design or interaction with |
|
|
550 | others. Oh, the pain, will it ever stop... |
407 | |
551 | |
408 | While stopping, setting and starting an I/O watcher in the same iteration |
552 | While stopping, setting and starting an I/O watcher in the same iteration |
409 | will result in some caching, there is still a system call per such |
553 | will result in some caching, there is still a system call per such |
410 | incident (because the same I<file descriptor> could point to a different |
554 | incident (because the same I<file descriptor> could point to a different |
411 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
555 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
418 | starting a watcher (without re-setting it) also usually doesn't cause |
562 | starting a watcher (without re-setting it) also usually doesn't cause |
419 | extra overhead. A fork can both result in spurious notifications as well |
563 | extra overhead. A fork can both result in spurious notifications as well |
420 | as in libev having to destroy and recreate the epoll object, which can |
564 | as in libev having to destroy and recreate the epoll object, which can |
421 | take considerable time and thus should be avoided. |
565 | take considerable time and thus should be avoided. |
422 | |
566 | |
|
|
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
569 | the usage. So sad. |
|
|
570 | |
423 | While nominally embeddable in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
424 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
573 | |
|
|
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
575 | C<EVBACKEND_POLL>. |
|
|
576 | |
|
|
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
578 | |
|
|
579 | Use the linux-specific linux aio (I<not> C<< aio(7) >>) event interface |
|
|
580 | available in post-4.18 kernels. |
|
|
581 | |
|
|
582 | If this backend works for you (as of this writing, it was very |
|
|
583 | experimental and only supports a subset of file types), it is the best |
|
|
584 | event interface available on linux and might be well worth it enabling it |
|
|
585 | - if it isn't available in your kernel this will be detected and another |
|
|
586 | backend will be chosen. |
|
|
587 | |
|
|
588 | This backend can batch oneshot requests and uses a user-space ring buffer |
|
|
589 | to receive events. It also doesn't suffer from most of the design problems |
|
|
590 | of epoll (such as not being able to remove event sources from the epoll |
|
|
591 | set), and generally sounds too good to be true. Because, this being the |
|
|
592 | linux kernel, of course it suffers from a whole new set of limitations. |
|
|
593 | |
|
|
594 | For one, it is not easily embeddable (but probably could be done using |
|
|
595 | an event fd at some extra overhead). It also is subject to various |
|
|
596 | arbitrary limits that can be configured in F</proc/sys/fs/aio-max-nr> |
|
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597 | and F</proc/sys/fs/aio-nr>), which could lead to it being skipped during |
|
|
598 | initialisation. |
|
|
599 | |
|
|
600 | Most problematic in practise, however, is that, like kqueue, it requires |
|
|
601 | special support from drivers, and, not surprisingly, not all drivers |
|
|
602 | implement it. For example, in linux 4.19, tcp sockets, pipes, event fds, |
|
|
603 | files, F</dev/null> and a few others are supported, but ttys are not, so |
|
|
604 | this is not (yet?) a generic event polling interface but is probably still |
|
|
605 | be very useful in a web server or similar program. |
425 | |
606 | |
426 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
607 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
427 | C<EVBACKEND_POLL>. |
608 | C<EVBACKEND_POLL>. |
428 | |
609 | |
429 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
610 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
… | |
… | |
444 | |
625 | |
445 | It scales in the same way as the epoll backend, but the interface to the |
626 | It scales in the same way as the epoll backend, but the interface to the |
446 | kernel is more efficient (which says nothing about its actual speed, of |
627 | kernel is more efficient (which says nothing about its actual speed, of |
447 | course). While stopping, setting and starting an I/O watcher does never |
628 | course). While stopping, setting and starting an I/O watcher does never |
448 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
629 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
449 | two event changes per incident. Support for C<fork ()> is very bad (but |
630 | two event changes per incident. Support for C<fork ()> is very bad (you |
450 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
631 | might have to leak fd's on fork, but it's more sane than epoll) and it |
451 | cases |
632 | drops fds silently in similarly hard-to-detect cases. |
452 | |
633 | |
453 | This backend usually performs well under most conditions. |
634 | This backend usually performs well under most conditions. |
454 | |
635 | |
455 | While nominally embeddable in other event loops, this doesn't work |
636 | While nominally embeddable in other event loops, this doesn't work |
456 | everywhere, so you might need to test for this. And since it is broken |
637 | everywhere, so you might need to test for this. And since it is broken |
457 | almost everywhere, you should only use it when you have a lot of sockets |
638 | almost everywhere, you should only use it when you have a lot of sockets |
458 | (for which it usually works), by embedding it into another event loop |
639 | (for which it usually works), by embedding it into another event loop |
459 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
640 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
460 | using it only for sockets. |
641 | also broken on OS X)) and, did I mention it, using it only for sockets. |
461 | |
642 | |
462 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
643 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
463 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
644 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
464 | C<NOTE_EOF>. |
645 | C<NOTE_EOF>. |
465 | |
646 | |
… | |
… | |
473 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
654 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
474 | |
655 | |
475 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
656 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
476 | it's really slow, but it still scales very well (O(active_fds)). |
657 | it's really slow, but it still scales very well (O(active_fds)). |
477 | |
658 | |
478 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
479 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
480 | blocking when no data (or space) is available. |
|
|
481 | |
|
|
482 | While this backend scales well, it requires one system call per active |
659 | While this backend scales well, it requires one system call per active |
483 | file descriptor per loop iteration. For small and medium numbers of file |
660 | file descriptor per loop iteration. For small and medium numbers of file |
484 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
661 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
485 | might perform better. |
662 | might perform better. |
486 | |
663 | |
487 | On the positive side, with the exception of the spurious readiness |
664 | On the positive side, this backend actually performed fully to |
488 | notifications, this backend actually performed fully to specification |
|
|
489 | in all tests and is fully embeddable, which is a rare feat among the |
665 | specification in all tests and is fully embeddable, which is a rare feat |
490 | OS-specific backends (I vastly prefer correctness over speed hacks). |
666 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
667 | hacks). |
|
|
668 | |
|
|
669 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
670 | even sun itself gets it wrong in their code examples: The event polling |
|
|
671 | function sometimes returns events to the caller even though an error |
|
|
672 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
673 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
674 | absolutely have to know whether an event occurred or not because you have |
|
|
675 | to re-arm the watcher. |
|
|
676 | |
|
|
677 | Fortunately libev seems to be able to work around these idiocies. |
491 | |
678 | |
492 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
679 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
493 | C<EVBACKEND_POLL>. |
680 | C<EVBACKEND_POLL>. |
494 | |
681 | |
495 | =item C<EVBACKEND_ALL> |
682 | =item C<EVBACKEND_ALL> |
496 | |
683 | |
497 | Try all backends (even potentially broken ones that wouldn't be tried |
684 | Try all backends (even potentially broken ones that wouldn't be tried |
498 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
685 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
499 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
686 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
500 | |
687 | |
501 | It is definitely not recommended to use this flag. |
688 | It is definitely not recommended to use this flag, use whatever |
|
|
689 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
690 | at all. |
|
|
691 | |
|
|
692 | =item C<EVBACKEND_MASK> |
|
|
693 | |
|
|
694 | Not a backend at all, but a mask to select all backend bits from a |
|
|
695 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
696 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
502 | |
697 | |
503 | =back |
698 | =back |
504 | |
699 | |
505 | If one or more of these are or'ed into the flags value, then only these |
700 | If one or more of the backend flags are or'ed into the flags value, |
506 | backends will be tried (in the reverse order as listed here). If none are |
701 | then only these backends will be tried (in the reverse order as listed |
507 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
702 | here). If none are specified, all backends in C<ev_recommended_backends |
508 | |
703 | ()> will be tried. |
509 | Example: This is the most typical usage. |
|
|
510 | |
|
|
511 | if (!ev_default_loop (0)) |
|
|
512 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
513 | |
|
|
514 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
515 | environment settings to be taken into account: |
|
|
516 | |
|
|
517 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
518 | |
|
|
519 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
520 | used if available (warning, breaks stuff, best use only with your own |
|
|
521 | private event loop and only if you know the OS supports your types of |
|
|
522 | fds): |
|
|
523 | |
|
|
524 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
525 | |
|
|
526 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
527 | |
|
|
528 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
529 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
530 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
531 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
532 | |
|
|
533 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
534 | libev with threads is indeed to create one loop per thread, and using the |
|
|
535 | default loop in the "main" or "initial" thread. |
|
|
536 | |
704 | |
537 | Example: Try to create a event loop that uses epoll and nothing else. |
705 | Example: Try to create a event loop that uses epoll and nothing else. |
538 | |
706 | |
539 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
707 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
540 | if (!epoller) |
708 | if (!epoller) |
541 | fatal ("no epoll found here, maybe it hides under your chair"); |
709 | fatal ("no epoll found here, maybe it hides under your chair"); |
542 | |
710 | |
|
|
711 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
712 | used if available. |
|
|
713 | |
|
|
714 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
715 | |
|
|
716 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
717 | linux aio backend if possible, but fall back to something else if that |
|
|
718 | isn't available. |
|
|
719 | |
|
|
720 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
721 | |
543 | =item ev_default_destroy () |
722 | =item ev_loop_destroy (loop) |
544 | |
723 | |
545 | Destroys the default loop again (frees all memory and kernel state |
724 | Destroys an event loop object (frees all memory and kernel state |
546 | etc.). None of the active event watchers will be stopped in the normal |
725 | etc.). None of the active event watchers will be stopped in the normal |
547 | sense, so e.g. C<ev_is_active> might still return true. It is your |
726 | sense, so e.g. C<ev_is_active> might still return true. It is your |
548 | responsibility to either stop all watchers cleanly yourself I<before> |
727 | responsibility to either stop all watchers cleanly yourself I<before> |
549 | calling this function, or cope with the fact afterwards (which is usually |
728 | calling this function, or cope with the fact afterwards (which is usually |
550 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
729 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
… | |
… | |
552 | |
731 | |
553 | Note that certain global state, such as signal state (and installed signal |
732 | Note that certain global state, such as signal state (and installed signal |
554 | handlers), will not be freed by this function, and related watchers (such |
733 | handlers), will not be freed by this function, and related watchers (such |
555 | as signal and child watchers) would need to be stopped manually. |
734 | as signal and child watchers) would need to be stopped manually. |
556 | |
735 | |
557 | In general it is not advisable to call this function except in the |
736 | This function is normally used on loop objects allocated by |
558 | rare occasion where you really need to free e.g. the signal handling |
737 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
738 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
739 | |
|
|
740 | Note that it is not advisable to call this function on the default loop |
|
|
741 | except in the rare occasion where you really need to free its resources. |
559 | pipe fds. If you need dynamically allocated loops it is better to use |
742 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
560 | C<ev_loop_new> and C<ev_loop_destroy>). |
743 | and C<ev_loop_destroy>. |
561 | |
744 | |
562 | =item ev_loop_destroy (loop) |
745 | =item ev_loop_fork (loop) |
563 | |
746 | |
564 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
565 | earlier call to C<ev_loop_new>. |
|
|
566 | |
|
|
567 | =item ev_default_fork () |
|
|
568 | |
|
|
569 | This function sets a flag that causes subsequent C<ev_loop> iterations |
747 | This function sets a flag that causes subsequent C<ev_run> iterations |
570 | to reinitialise the kernel state for backends that have one. Despite the |
748 | to reinitialise the kernel state for backends that have one. Despite |
571 | name, you can call it anytime, but it makes most sense after forking, in |
749 | the name, you can call it anytime you are allowed to start or stop |
572 | the child process (or both child and parent, but that again makes little |
750 | watchers (except inside an C<ev_prepare> callback), but it makes most |
573 | sense). You I<must> call it in the child before using any of the libev |
751 | sense after forking, in the child process. You I<must> call it (or use |
574 | functions, and it will only take effect at the next C<ev_loop> iteration. |
752 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
753 | |
|
|
754 | In addition, if you want to reuse a loop (via this function or |
|
|
755 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
756 | |
|
|
757 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
758 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
759 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
760 | during fork. |
575 | |
761 | |
576 | On the other hand, you only need to call this function in the child |
762 | On the other hand, you only need to call this function in the child |
577 | process if and only if you want to use the event library in the child. If |
763 | process if and only if you want to use the event loop in the child. If |
578 | you just fork+exec, you don't have to call it at all. |
764 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
765 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
766 | difference, but libev will usually detect this case on its own and do a |
|
|
767 | costly reset of the backend). |
579 | |
768 | |
580 | The function itself is quite fast and it's usually not a problem to call |
769 | The function itself is quite fast and it's usually not a problem to call |
581 | it just in case after a fork. To make this easy, the function will fit in |
770 | it just in case after a fork. |
582 | quite nicely into a call to C<pthread_atfork>: |
|
|
583 | |
771 | |
|
|
772 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
773 | using pthreads. |
|
|
774 | |
|
|
775 | static void |
|
|
776 | post_fork_child (void) |
|
|
777 | { |
|
|
778 | ev_loop_fork (EV_DEFAULT); |
|
|
779 | } |
|
|
780 | |
|
|
781 | ... |
584 | pthread_atfork (0, 0, ev_default_fork); |
782 | pthread_atfork (0, 0, post_fork_child); |
585 | |
|
|
586 | =item ev_loop_fork (loop) |
|
|
587 | |
|
|
588 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
589 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
590 | after fork that you want to re-use in the child, and how you do this is |
|
|
591 | entirely your own problem. |
|
|
592 | |
783 | |
593 | =item int ev_is_default_loop (loop) |
784 | =item int ev_is_default_loop (loop) |
594 | |
785 | |
595 | Returns true when the given loop is, in fact, the default loop, and false |
786 | Returns true when the given loop is, in fact, the default loop, and false |
596 | otherwise. |
787 | otherwise. |
597 | |
788 | |
598 | =item unsigned int ev_loop_count (loop) |
789 | =item unsigned int ev_iteration (loop) |
599 | |
790 | |
600 | Returns the count of loop iterations for the loop, which is identical to |
791 | Returns the current iteration count for the event loop, which is identical |
601 | the number of times libev did poll for new events. It starts at C<0> and |
792 | to the number of times libev did poll for new events. It starts at C<0> |
602 | happily wraps around with enough iterations. |
793 | and happily wraps around with enough iterations. |
603 | |
794 | |
604 | This value can sometimes be useful as a generation counter of sorts (it |
795 | This value can sometimes be useful as a generation counter of sorts (it |
605 | "ticks" the number of loop iterations), as it roughly corresponds with |
796 | "ticks" the number of loop iterations), as it roughly corresponds with |
606 | C<ev_prepare> and C<ev_check> calls. |
797 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
798 | prepare and check phases. |
|
|
799 | |
|
|
800 | =item unsigned int ev_depth (loop) |
|
|
801 | |
|
|
802 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
803 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
804 | |
|
|
805 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
806 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
807 | in which case it is higher. |
|
|
808 | |
|
|
809 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
810 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
811 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
812 | convenient, in which case it is fully supported. |
607 | |
813 | |
608 | =item unsigned int ev_backend (loop) |
814 | =item unsigned int ev_backend (loop) |
609 | |
815 | |
610 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
816 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
611 | use. |
817 | use. |
… | |
… | |
620 | |
826 | |
621 | =item ev_now_update (loop) |
827 | =item ev_now_update (loop) |
622 | |
828 | |
623 | Establishes the current time by querying the kernel, updating the time |
829 | Establishes the current time by querying the kernel, updating the time |
624 | returned by C<ev_now ()> in the progress. This is a costly operation and |
830 | returned by C<ev_now ()> in the progress. This is a costly operation and |
625 | is usually done automatically within C<ev_loop ()>. |
831 | is usually done automatically within C<ev_run ()>. |
626 | |
832 | |
627 | This function is rarely useful, but when some event callback runs for a |
833 | This function is rarely useful, but when some event callback runs for a |
628 | very long time without entering the event loop, updating libev's idea of |
834 | very long time without entering the event loop, updating libev's idea of |
629 | the current time is a good idea. |
835 | the current time is a good idea. |
630 | |
836 | |
631 | See also "The special problem of time updates" in the C<ev_timer> section. |
837 | See also L</The special problem of time updates> in the C<ev_timer> section. |
632 | |
838 | |
|
|
839 | =item ev_suspend (loop) |
|
|
840 | |
|
|
841 | =item ev_resume (loop) |
|
|
842 | |
|
|
843 | These two functions suspend and resume an event loop, for use when the |
|
|
844 | loop is not used for a while and timeouts should not be processed. |
|
|
845 | |
|
|
846 | A typical use case would be an interactive program such as a game: When |
|
|
847 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
848 | would be best to handle timeouts as if no time had actually passed while |
|
|
849 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
850 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
851 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
852 | |
|
|
853 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
854 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
855 | will be rescheduled (that is, they will lose any events that would have |
|
|
856 | occurred while suspended). |
|
|
857 | |
|
|
858 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
859 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
860 | without a previous call to C<ev_suspend>. |
|
|
861 | |
|
|
862 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
863 | event loop time (see C<ev_now_update>). |
|
|
864 | |
633 | =item ev_loop (loop, int flags) |
865 | =item bool ev_run (loop, int flags) |
634 | |
866 | |
635 | Finally, this is it, the event handler. This function usually is called |
867 | Finally, this is it, the event handler. This function usually is called |
636 | after you initialised all your watchers and you want to start handling |
868 | after you have initialised all your watchers and you want to start |
637 | events. |
869 | handling events. It will ask the operating system for any new events, call |
|
|
870 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
871 | is why event loops are called I<loops>. |
638 | |
872 | |
639 | If the flags argument is specified as C<0>, it will not return until |
873 | If the flags argument is specified as C<0>, it will keep handling events |
640 | either no event watchers are active anymore or C<ev_unloop> was called. |
874 | until either no event watchers are active anymore or C<ev_break> was |
|
|
875 | called. |
641 | |
876 | |
|
|
877 | The return value is false if there are no more active watchers (which |
|
|
878 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
879 | (which usually means " you should call C<ev_run> again"). |
|
|
880 | |
642 | Please note that an explicit C<ev_unloop> is usually better than |
881 | Please note that an explicit C<ev_break> is usually better than |
643 | relying on all watchers to be stopped when deciding when a program has |
882 | relying on all watchers to be stopped when deciding when a program has |
644 | finished (especially in interactive programs), but having a program |
883 | finished (especially in interactive programs), but having a program |
645 | that automatically loops as long as it has to and no longer by virtue |
884 | that automatically loops as long as it has to and no longer by virtue |
646 | of relying on its watchers stopping correctly, that is truly a thing of |
885 | of relying on its watchers stopping correctly, that is truly a thing of |
647 | beauty. |
886 | beauty. |
648 | |
887 | |
|
|
888 | This function is I<mostly> exception-safe - you can break out of a |
|
|
889 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
890 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
891 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
892 | |
649 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
893 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
650 | those events and any already outstanding ones, but will not block your |
894 | those events and any already outstanding ones, but will not wait and |
651 | process in case there are no events and will return after one iteration of |
895 | block your process in case there are no events and will return after one |
652 | the loop. |
896 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
897 | events while doing lengthy calculations, to keep the program responsive. |
653 | |
898 | |
654 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
899 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
655 | necessary) and will handle those and any already outstanding ones. It |
900 | necessary) and will handle those and any already outstanding ones. It |
656 | will block your process until at least one new event arrives (which could |
901 | will block your process until at least one new event arrives (which could |
657 | be an event internal to libev itself, so there is no guarantee that a |
902 | be an event internal to libev itself, so there is no guarantee that a |
658 | user-registered callback will be called), and will return after one |
903 | user-registered callback will be called), and will return after one |
659 | iteration of the loop. |
904 | iteration of the loop. |
660 | |
905 | |
661 | This is useful if you are waiting for some external event in conjunction |
906 | This is useful if you are waiting for some external event in conjunction |
662 | with something not expressible using other libev watchers (i.e. "roll your |
907 | with something not expressible using other libev watchers (i.e. "roll your |
663 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
908 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
664 | usually a better approach for this kind of thing. |
909 | usually a better approach for this kind of thing. |
665 | |
910 | |
666 | Here are the gory details of what C<ev_loop> does: |
911 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
912 | understanding, not a guarantee that things will work exactly like this in |
|
|
913 | future versions): |
667 | |
914 | |
|
|
915 | - Increment loop depth. |
|
|
916 | - Reset the ev_break status. |
668 | - Before the first iteration, call any pending watchers. |
917 | - Before the first iteration, call any pending watchers. |
|
|
918 | LOOP: |
669 | * If EVFLAG_FORKCHECK was used, check for a fork. |
919 | - If EVFLAG_FORKCHECK was used, check for a fork. |
670 | - If a fork was detected (by any means), queue and call all fork watchers. |
920 | - If a fork was detected (by any means), queue and call all fork watchers. |
671 | - Queue and call all prepare watchers. |
921 | - Queue and call all prepare watchers. |
|
|
922 | - If ev_break was called, goto FINISH. |
672 | - If we have been forked, detach and recreate the kernel state |
923 | - If we have been forked, detach and recreate the kernel state |
673 | as to not disturb the other process. |
924 | as to not disturb the other process. |
674 | - Update the kernel state with all outstanding changes. |
925 | - Update the kernel state with all outstanding changes. |
675 | - Update the "event loop time" (ev_now ()). |
926 | - Update the "event loop time" (ev_now ()). |
676 | - Calculate for how long to sleep or block, if at all |
927 | - Calculate for how long to sleep or block, if at all |
677 | (active idle watchers, EVLOOP_NONBLOCK or not having |
928 | (active idle watchers, EVRUN_NOWAIT or not having |
678 | any active watchers at all will result in not sleeping). |
929 | any active watchers at all will result in not sleeping). |
679 | - Sleep if the I/O and timer collect interval say so. |
930 | - Sleep if the I/O and timer collect interval say so. |
|
|
931 | - Increment loop iteration counter. |
680 | - Block the process, waiting for any events. |
932 | - Block the process, waiting for any events. |
681 | - Queue all outstanding I/O (fd) events. |
933 | - Queue all outstanding I/O (fd) events. |
682 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
934 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
683 | - Queue all expired timers. |
935 | - Queue all expired timers. |
684 | - Queue all expired periodics. |
936 | - Queue all expired periodics. |
685 | - Unless any events are pending now, queue all idle watchers. |
937 | - Queue all idle watchers with priority higher than that of pending events. |
686 | - Queue all check watchers. |
938 | - Queue all check watchers. |
687 | - Call all queued watchers in reverse order (i.e. check watchers first). |
939 | - Call all queued watchers in reverse order (i.e. check watchers first). |
688 | Signals and child watchers are implemented as I/O watchers, and will |
940 | Signals and child watchers are implemented as I/O watchers, and will |
689 | be handled here by queueing them when their watcher gets executed. |
941 | be handled here by queueing them when their watcher gets executed. |
690 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
942 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
691 | were used, or there are no active watchers, return, otherwise |
943 | were used, or there are no active watchers, goto FINISH, otherwise |
692 | continue with step *. |
944 | continue with step LOOP. |
|
|
945 | FINISH: |
|
|
946 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
947 | - Decrement the loop depth. |
|
|
948 | - Return. |
693 | |
949 | |
694 | Example: Queue some jobs and then loop until no events are outstanding |
950 | Example: Queue some jobs and then loop until no events are outstanding |
695 | anymore. |
951 | anymore. |
696 | |
952 | |
697 | ... queue jobs here, make sure they register event watchers as long |
953 | ... queue jobs here, make sure they register event watchers as long |
698 | ... as they still have work to do (even an idle watcher will do..) |
954 | ... as they still have work to do (even an idle watcher will do..) |
699 | ev_loop (my_loop, 0); |
955 | ev_run (my_loop, 0); |
700 | ... jobs done or somebody called unloop. yeah! |
956 | ... jobs done or somebody called break. yeah! |
701 | |
957 | |
702 | =item ev_unloop (loop, how) |
958 | =item ev_break (loop, how) |
703 | |
959 | |
704 | Can be used to make a call to C<ev_loop> return early (but only after it |
960 | Can be used to make a call to C<ev_run> return early (but only after it |
705 | has processed all outstanding events). The C<how> argument must be either |
961 | has processed all outstanding events). The C<how> argument must be either |
706 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
962 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
707 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
963 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
708 | |
964 | |
709 | This "unloop state" will be cleared when entering C<ev_loop> again. |
965 | This "break state" will be cleared on the next call to C<ev_run>. |
710 | |
966 | |
711 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
967 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
968 | which case it will have no effect. |
712 | |
969 | |
713 | =item ev_ref (loop) |
970 | =item ev_ref (loop) |
714 | |
971 | |
715 | =item ev_unref (loop) |
972 | =item ev_unref (loop) |
716 | |
973 | |
717 | Ref/unref can be used to add or remove a reference count on the event |
974 | Ref/unref can be used to add or remove a reference count on the event |
718 | loop: Every watcher keeps one reference, and as long as the reference |
975 | loop: Every watcher keeps one reference, and as long as the reference |
719 | count is nonzero, C<ev_loop> will not return on its own. |
976 | count is nonzero, C<ev_run> will not return on its own. |
720 | |
977 | |
721 | If you have a watcher you never unregister that should not keep C<ev_loop> |
978 | This is useful when you have a watcher that you never intend to |
722 | from returning, call ev_unref() after starting, and ev_ref() before |
979 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
980 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
723 | stopping it. |
981 | before stopping it. |
724 | |
982 | |
725 | As an example, libev itself uses this for its internal signal pipe: It is |
983 | As an example, libev itself uses this for its internal signal pipe: It |
726 | not visible to the libev user and should not keep C<ev_loop> from exiting |
984 | is not visible to the libev user and should not keep C<ev_run> from |
727 | if no event watchers registered by it are active. It is also an excellent |
985 | exiting if no event watchers registered by it are active. It is also an |
728 | way to do this for generic recurring timers or from within third-party |
986 | excellent way to do this for generic recurring timers or from within |
729 | libraries. Just remember to I<unref after start> and I<ref before stop> |
987 | third-party libraries. Just remember to I<unref after start> and I<ref |
730 | (but only if the watcher wasn't active before, or was active before, |
988 | before stop> (but only if the watcher wasn't active before, or was active |
731 | respectively). |
989 | before, respectively. Note also that libev might stop watchers itself |
|
|
990 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
991 | in the callback). |
732 | |
992 | |
733 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
993 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
734 | running when nothing else is active. |
994 | running when nothing else is active. |
735 | |
995 | |
736 | ev_signal exitsig; |
996 | ev_signal exitsig; |
737 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
997 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
738 | ev_signal_start (loop, &exitsig); |
998 | ev_signal_start (loop, &exitsig); |
739 | evf_unref (loop); |
999 | ev_unref (loop); |
740 | |
1000 | |
741 | Example: For some weird reason, unregister the above signal handler again. |
1001 | Example: For some weird reason, unregister the above signal handler again. |
742 | |
1002 | |
743 | ev_ref (loop); |
1003 | ev_ref (loop); |
744 | ev_signal_stop (loop, &exitsig); |
1004 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
764 | overhead for the actual polling but can deliver many events at once. |
1024 | overhead for the actual polling but can deliver many events at once. |
765 | |
1025 | |
766 | By setting a higher I<io collect interval> you allow libev to spend more |
1026 | By setting a higher I<io collect interval> you allow libev to spend more |
767 | time collecting I/O events, so you can handle more events per iteration, |
1027 | time collecting I/O events, so you can handle more events per iteration, |
768 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1028 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
769 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1029 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
770 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
1030 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
1031 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
1032 | once per this interval, on average (as long as the host time resolution is |
|
|
1033 | good enough). |
771 | |
1034 | |
772 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1035 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
773 | to spend more time collecting timeouts, at the expense of increased |
1036 | to spend more time collecting timeouts, at the expense of increased |
774 | latency/jitter/inexactness (the watcher callback will be called |
1037 | latency/jitter/inexactness (the watcher callback will be called |
775 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
1038 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
777 | |
1040 | |
778 | Many (busy) programs can usually benefit by setting the I/O collect |
1041 | Many (busy) programs can usually benefit by setting the I/O collect |
779 | interval to a value near C<0.1> or so, which is often enough for |
1042 | interval to a value near C<0.1> or so, which is often enough for |
780 | interactive servers (of course not for games), likewise for timeouts. It |
1043 | interactive servers (of course not for games), likewise for timeouts. It |
781 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
1044 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
782 | as this approaches the timing granularity of most systems. |
1045 | as this approaches the timing granularity of most systems. Note that if |
|
|
1046 | you do transactions with the outside world and you can't increase the |
|
|
1047 | parallelity, then this setting will limit your transaction rate (if you |
|
|
1048 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
1049 | then you can't do more than 100 transactions per second). |
783 | |
1050 | |
784 | Setting the I<timeout collect interval> can improve the opportunity for |
1051 | Setting the I<timeout collect interval> can improve the opportunity for |
785 | saving power, as the program will "bundle" timer callback invocations that |
1052 | saving power, as the program will "bundle" timer callback invocations that |
786 | are "near" in time together, by delaying some, thus reducing the number of |
1053 | are "near" in time together, by delaying some, thus reducing the number of |
787 | times the process sleeps and wakes up again. Another useful technique to |
1054 | times the process sleeps and wakes up again. Another useful technique to |
788 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
1055 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
789 | they fire on, say, one-second boundaries only. |
1056 | they fire on, say, one-second boundaries only. |
790 | |
1057 | |
|
|
1058 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
1059 | more often than 100 times per second: |
|
|
1060 | |
|
|
1061 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
1062 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
1063 | |
|
|
1064 | =item ev_invoke_pending (loop) |
|
|
1065 | |
|
|
1066 | This call will simply invoke all pending watchers while resetting their |
|
|
1067 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
1068 | but when overriding the invoke callback this call comes handy. This |
|
|
1069 | function can be invoked from a watcher - this can be useful for example |
|
|
1070 | when you want to do some lengthy calculation and want to pass further |
|
|
1071 | event handling to another thread (you still have to make sure only one |
|
|
1072 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1073 | |
|
|
1074 | =item int ev_pending_count (loop) |
|
|
1075 | |
|
|
1076 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1077 | are pending. |
|
|
1078 | |
|
|
1079 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1080 | |
|
|
1081 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1082 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1083 | this callback instead. This is useful, for example, when you want to |
|
|
1084 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1085 | |
|
|
1086 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1087 | callback. |
|
|
1088 | |
|
|
1089 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
|
|
1090 | |
|
|
1091 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1092 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1093 | each call to a libev function. |
|
|
1094 | |
|
|
1095 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1096 | to wait for it to return. One way around this is to wake up the event |
|
|
1097 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
|
|
1098 | I<release> and I<acquire> callbacks on the loop. |
|
|
1099 | |
|
|
1100 | When set, then C<release> will be called just before the thread is |
|
|
1101 | suspended waiting for new events, and C<acquire> is called just |
|
|
1102 | afterwards. |
|
|
1103 | |
|
|
1104 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1105 | C<acquire> will just call the mutex_lock function again. |
|
|
1106 | |
|
|
1107 | While event loop modifications are allowed between invocations of |
|
|
1108 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1109 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1110 | have no effect on the set of file descriptors being watched, or the time |
|
|
1111 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1112 | to take note of any changes you made. |
|
|
1113 | |
|
|
1114 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1115 | invocations of C<release> and C<acquire>. |
|
|
1116 | |
|
|
1117 | See also the locking example in the C<THREADS> section later in this |
|
|
1118 | document. |
|
|
1119 | |
|
|
1120 | =item ev_set_userdata (loop, void *data) |
|
|
1121 | |
|
|
1122 | =item void *ev_userdata (loop) |
|
|
1123 | |
|
|
1124 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1125 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1126 | C<0>. |
|
|
1127 | |
|
|
1128 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1129 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1130 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1131 | any other purpose as well. |
|
|
1132 | |
791 | =item ev_loop_verify (loop) |
1133 | =item ev_verify (loop) |
792 | |
1134 | |
793 | This function only does something when C<EV_VERIFY> support has been |
1135 | This function only does something when C<EV_VERIFY> support has been |
794 | compiled in, which is the default for non-minimal builds. It tries to go |
1136 | compiled in, which is the default for non-minimal builds. It tries to go |
795 | through all internal structures and checks them for validity. If anything |
1137 | through all internal structures and checks them for validity. If anything |
796 | is found to be inconsistent, it will print an error message to standard |
1138 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
807 | |
1149 | |
808 | In the following description, uppercase C<TYPE> in names stands for the |
1150 | In the following description, uppercase C<TYPE> in names stands for the |
809 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1151 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
810 | watchers and C<ev_io_start> for I/O watchers. |
1152 | watchers and C<ev_io_start> for I/O watchers. |
811 | |
1153 | |
812 | A watcher is a structure that you create and register to record your |
1154 | A watcher is an opaque structure that you allocate and register to record |
813 | interest in some event. For instance, if you want to wait for STDIN to |
1155 | your interest in some event. To make a concrete example, imagine you want |
814 | become readable, you would create an C<ev_io> watcher for that: |
1156 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1157 | for that: |
815 | |
1158 | |
816 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1159 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
817 | { |
1160 | { |
818 | ev_io_stop (w); |
1161 | ev_io_stop (w); |
819 | ev_unloop (loop, EVUNLOOP_ALL); |
1162 | ev_break (loop, EVBREAK_ALL); |
820 | } |
1163 | } |
821 | |
1164 | |
822 | struct ev_loop *loop = ev_default_loop (0); |
1165 | struct ev_loop *loop = ev_default_loop (0); |
823 | |
1166 | |
824 | ev_io stdin_watcher; |
1167 | ev_io stdin_watcher; |
825 | |
1168 | |
826 | ev_init (&stdin_watcher, my_cb); |
1169 | ev_init (&stdin_watcher, my_cb); |
827 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1170 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
828 | ev_io_start (loop, &stdin_watcher); |
1171 | ev_io_start (loop, &stdin_watcher); |
829 | |
1172 | |
830 | ev_loop (loop, 0); |
1173 | ev_run (loop, 0); |
831 | |
1174 | |
832 | As you can see, you are responsible for allocating the memory for your |
1175 | As you can see, you are responsible for allocating the memory for your |
833 | watcher structures (and it is I<usually> a bad idea to do this on the |
1176 | watcher structures (and it is I<usually> a bad idea to do this on the |
834 | stack). |
1177 | stack). |
835 | |
1178 | |
836 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1179 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
837 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1180 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
838 | |
1181 | |
839 | Each watcher structure must be initialised by a call to C<ev_init |
1182 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
840 | (watcher *, callback)>, which expects a callback to be provided. This |
1183 | *, callback)>, which expects a callback to be provided. This callback is |
841 | callback gets invoked each time the event occurs (or, in the case of I/O |
1184 | invoked each time the event occurs (or, in the case of I/O watchers, each |
842 | watchers, each time the event loop detects that the file descriptor given |
1185 | time the event loop detects that the file descriptor given is readable |
843 | is readable and/or writable). |
1186 | and/or writable). |
844 | |
1187 | |
845 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1188 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
846 | macro to configure it, with arguments specific to the watcher type. There |
1189 | macro to configure it, with arguments specific to the watcher type. There |
847 | is also a macro to combine initialisation and setting in one call: C<< |
1190 | is also a macro to combine initialisation and setting in one call: C<< |
848 | ev_TYPE_init (watcher *, callback, ...) >>. |
1191 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
871 | =item C<EV_WRITE> |
1214 | =item C<EV_WRITE> |
872 | |
1215 | |
873 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1216 | The file descriptor in the C<ev_io> watcher has become readable and/or |
874 | writable. |
1217 | writable. |
875 | |
1218 | |
876 | =item C<EV_TIMEOUT> |
1219 | =item C<EV_TIMER> |
877 | |
1220 | |
878 | The C<ev_timer> watcher has timed out. |
1221 | The C<ev_timer> watcher has timed out. |
879 | |
1222 | |
880 | =item C<EV_PERIODIC> |
1223 | =item C<EV_PERIODIC> |
881 | |
1224 | |
… | |
… | |
899 | |
1242 | |
900 | =item C<EV_PREPARE> |
1243 | =item C<EV_PREPARE> |
901 | |
1244 | |
902 | =item C<EV_CHECK> |
1245 | =item C<EV_CHECK> |
903 | |
1246 | |
904 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1247 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
905 | to gather new events, and all C<ev_check> watchers are invoked just after |
1248 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
906 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1249 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1250 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1251 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1252 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1253 | or lower priority within an event loop iteration. |
|
|
1254 | |
907 | received events. Callbacks of both watcher types can start and stop as |
1255 | Callbacks of both watcher types can start and stop as many watchers as |
908 | many watchers as they want, and all of them will be taken into account |
1256 | they want, and all of them will be taken into account (for example, a |
909 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1257 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
910 | C<ev_loop> from blocking). |
1258 | blocking). |
911 | |
1259 | |
912 | =item C<EV_EMBED> |
1260 | =item C<EV_EMBED> |
913 | |
1261 | |
914 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1262 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
915 | |
1263 | |
916 | =item C<EV_FORK> |
1264 | =item C<EV_FORK> |
917 | |
1265 | |
918 | The event loop has been resumed in the child process after fork (see |
1266 | The event loop has been resumed in the child process after fork (see |
919 | C<ev_fork>). |
1267 | C<ev_fork>). |
920 | |
1268 | |
|
|
1269 | =item C<EV_CLEANUP> |
|
|
1270 | |
|
|
1271 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1272 | |
921 | =item C<EV_ASYNC> |
1273 | =item C<EV_ASYNC> |
922 | |
1274 | |
923 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1275 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1276 | |
|
|
1277 | =item C<EV_CUSTOM> |
|
|
1278 | |
|
|
1279 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1280 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
924 | |
1281 | |
925 | =item C<EV_ERROR> |
1282 | =item C<EV_ERROR> |
926 | |
1283 | |
927 | An unspecified error has occurred, the watcher has been stopped. This might |
1284 | An unspecified error has occurred, the watcher has been stopped. This might |
928 | happen because the watcher could not be properly started because libev |
1285 | happen because the watcher could not be properly started because libev |
… | |
… | |
966 | |
1323 | |
967 | ev_io w; |
1324 | ev_io w; |
968 | ev_init (&w, my_cb); |
1325 | ev_init (&w, my_cb); |
969 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1326 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
970 | |
1327 | |
971 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1328 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
972 | |
1329 | |
973 | This macro initialises the type-specific parts of a watcher. You need to |
1330 | This macro initialises the type-specific parts of a watcher. You need to |
974 | call C<ev_init> at least once before you call this macro, but you can |
1331 | call C<ev_init> at least once before you call this macro, but you can |
975 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1332 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
976 | macro on a watcher that is active (it can be pending, however, which is a |
1333 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
989 | |
1346 | |
990 | Example: Initialise and set an C<ev_io> watcher in one step. |
1347 | Example: Initialise and set an C<ev_io> watcher in one step. |
991 | |
1348 | |
992 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1349 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
993 | |
1350 | |
994 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1351 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
995 | |
1352 | |
996 | Starts (activates) the given watcher. Only active watchers will receive |
1353 | Starts (activates) the given watcher. Only active watchers will receive |
997 | events. If the watcher is already active nothing will happen. |
1354 | events. If the watcher is already active nothing will happen. |
998 | |
1355 | |
999 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1356 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1000 | whole section. |
1357 | whole section. |
1001 | |
1358 | |
1002 | ev_io_start (EV_DEFAULT_UC, &w); |
1359 | ev_io_start (EV_DEFAULT_UC, &w); |
1003 | |
1360 | |
1004 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1361 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1005 | |
1362 | |
1006 | Stops the given watcher if active, and clears the pending status (whether |
1363 | Stops the given watcher if active, and clears the pending status (whether |
1007 | the watcher was active or not). |
1364 | the watcher was active or not). |
1008 | |
1365 | |
1009 | It is possible that stopped watchers are pending - for example, |
1366 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1029 | |
1386 | |
1030 | =item callback ev_cb (ev_TYPE *watcher) |
1387 | =item callback ev_cb (ev_TYPE *watcher) |
1031 | |
1388 | |
1032 | Returns the callback currently set on the watcher. |
1389 | Returns the callback currently set on the watcher. |
1033 | |
1390 | |
1034 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1391 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1035 | |
1392 | |
1036 | Change the callback. You can change the callback at virtually any time |
1393 | Change the callback. You can change the callback at virtually any time |
1037 | (modulo threads). |
1394 | (modulo threads). |
1038 | |
1395 | |
1039 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1396 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1040 | |
1397 | |
1041 | =item int ev_priority (ev_TYPE *watcher) |
1398 | =item int ev_priority (ev_TYPE *watcher) |
1042 | |
1399 | |
1043 | Set and query the priority of the watcher. The priority is a small |
1400 | Set and query the priority of the watcher. The priority is a small |
1044 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1401 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1045 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1402 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1046 | before watchers with lower priority, but priority will not keep watchers |
1403 | before watchers with lower priority, but priority will not keep watchers |
1047 | from being executed (except for C<ev_idle> watchers). |
1404 | from being executed (except for C<ev_idle> watchers). |
1048 | |
1405 | |
1049 | This means that priorities are I<only> used for ordering callback |
|
|
1050 | invocation after new events have been received. This is useful, for |
|
|
1051 | example, to reduce latency after idling, or more often, to bind two |
|
|
1052 | watchers on the same event and make sure one is called first. |
|
|
1053 | |
|
|
1054 | If you need to suppress invocation when higher priority events are pending |
1406 | If you need to suppress invocation when higher priority events are pending |
1055 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1407 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1056 | |
1408 | |
1057 | You I<must not> change the priority of a watcher as long as it is active or |
1409 | You I<must not> change the priority of a watcher as long as it is active or |
1058 | pending. |
1410 | pending. |
1059 | |
|
|
1060 | The default priority used by watchers when no priority has been set is |
|
|
1061 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1062 | |
1411 | |
1063 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1412 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1064 | fine, as long as you do not mind that the priority value you query might |
1413 | fine, as long as you do not mind that the priority value you query might |
1065 | or might not have been clamped to the valid range. |
1414 | or might not have been clamped to the valid range. |
|
|
1415 | |
|
|
1416 | The default priority used by watchers when no priority has been set is |
|
|
1417 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1418 | |
|
|
1419 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1420 | priorities. |
1066 | |
1421 | |
1067 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1422 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1068 | |
1423 | |
1069 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1424 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1070 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1425 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1078 | watcher isn't pending it does nothing and returns C<0>. |
1433 | watcher isn't pending it does nothing and returns C<0>. |
1079 | |
1434 | |
1080 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1435 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1081 | callback to be invoked, which can be accomplished with this function. |
1436 | callback to be invoked, which can be accomplished with this function. |
1082 | |
1437 | |
|
|
1438 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1439 | |
|
|
1440 | Feeds the given event set into the event loop, as if the specified event |
|
|
1441 | had happened for the specified watcher (which must be a pointer to an |
|
|
1442 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1443 | not free the watcher as long as it has pending events. |
|
|
1444 | |
|
|
1445 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1446 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1447 | not started in the first place. |
|
|
1448 | |
|
|
1449 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1450 | functions that do not need a watcher. |
|
|
1451 | |
1083 | =back |
1452 | =back |
1084 | |
1453 | |
|
|
1454 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1455 | OWN COMPOSITE WATCHERS> idioms. |
1085 | |
1456 | |
1086 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1457 | =head2 WATCHER STATES |
1087 | |
1458 | |
1088 | Each watcher has, by default, a member C<void *data> that you can change |
1459 | There are various watcher states mentioned throughout this manual - |
1089 | and read at any time: libev will completely ignore it. This can be used |
1460 | active, pending and so on. In this section these states and the rules to |
1090 | to associate arbitrary data with your watcher. If you need more data and |
1461 | transition between them will be described in more detail - and while these |
1091 | don't want to allocate memory and store a pointer to it in that data |
1462 | rules might look complicated, they usually do "the right thing". |
1092 | member, you can also "subclass" the watcher type and provide your own |
|
|
1093 | data: |
|
|
1094 | |
1463 | |
1095 | struct my_io |
1464 | =over 4 |
|
|
1465 | |
|
|
1466 | =item initialised |
|
|
1467 | |
|
|
1468 | Before a watcher can be registered with the event loop it has to be |
|
|
1469 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1470 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1471 | |
|
|
1472 | In this state it is simply some block of memory that is suitable for |
|
|
1473 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1474 | will - as long as you either keep the memory contents intact, or call |
|
|
1475 | C<ev_TYPE_init> again. |
|
|
1476 | |
|
|
1477 | =item started/running/active |
|
|
1478 | |
|
|
1479 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1480 | property of the event loop, and is actively waiting for events. While in |
|
|
1481 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1482 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1483 | and call libev functions on it that are documented to work on active watchers. |
|
|
1484 | |
|
|
1485 | =item pending |
|
|
1486 | |
|
|
1487 | If a watcher is active and libev determines that an event it is interested |
|
|
1488 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1489 | stay in this pending state until either it is stopped or its callback is |
|
|
1490 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1491 | callback. |
|
|
1492 | |
|
|
1493 | The watcher might or might not be active while it is pending (for example, |
|
|
1494 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1495 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1496 | but it is still property of the event loop at this time, so cannot be |
|
|
1497 | moved, freed or reused. And if it is active the rules described in the |
|
|
1498 | previous item still apply. |
|
|
1499 | |
|
|
1500 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1501 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1502 | active. |
|
|
1503 | |
|
|
1504 | =item stopped |
|
|
1505 | |
|
|
1506 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1507 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1508 | latter will clear any pending state the watcher might be in, regardless |
|
|
1509 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1510 | freeing it is often a good idea. |
|
|
1511 | |
|
|
1512 | While stopped (and not pending) the watcher is essentially in the |
|
|
1513 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1514 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1515 | it again). |
|
|
1516 | |
|
|
1517 | =back |
|
|
1518 | |
|
|
1519 | =head2 WATCHER PRIORITY MODELS |
|
|
1520 | |
|
|
1521 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1522 | integers that influence the ordering of event callback invocation |
|
|
1523 | between watchers in some way, all else being equal. |
|
|
1524 | |
|
|
1525 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1526 | description for the more technical details such as the actual priority |
|
|
1527 | range. |
|
|
1528 | |
|
|
1529 | There are two common ways how these these priorities are being interpreted |
|
|
1530 | by event loops: |
|
|
1531 | |
|
|
1532 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1533 | of lower priority watchers, which means as long as higher priority |
|
|
1534 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1535 | |
|
|
1536 | The less common only-for-ordering model uses priorities solely to order |
|
|
1537 | callback invocation within a single event loop iteration: Higher priority |
|
|
1538 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1539 | before polling for new events. |
|
|
1540 | |
|
|
1541 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1542 | except for idle watchers (which use the lock-out model). |
|
|
1543 | |
|
|
1544 | The rationale behind this is that implementing the lock-out model for |
|
|
1545 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1546 | libraries will just poll for the same events again and again as long as |
|
|
1547 | their callbacks have not been executed, which is very inefficient in the |
|
|
1548 | common case of one high-priority watcher locking out a mass of lower |
|
|
1549 | priority ones. |
|
|
1550 | |
|
|
1551 | Static (ordering) priorities are most useful when you have two or more |
|
|
1552 | watchers handling the same resource: a typical usage example is having an |
|
|
1553 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1554 | timeouts. Under load, data might be received while the program handles |
|
|
1555 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1556 | handler will be executed before checking for data. In that case, giving |
|
|
1557 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1558 | handled first even under adverse conditions (which is usually, but not |
|
|
1559 | always, what you want). |
|
|
1560 | |
|
|
1561 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1562 | will only be executed when no same or higher priority watchers have |
|
|
1563 | received events, they can be used to implement the "lock-out" model when |
|
|
1564 | required. |
|
|
1565 | |
|
|
1566 | For example, to emulate how many other event libraries handle priorities, |
|
|
1567 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1568 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1569 | processing is done in the idle watcher callback. This causes libev to |
|
|
1570 | continuously poll and process kernel event data for the watcher, but when |
|
|
1571 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1572 | workable. |
|
|
1573 | |
|
|
1574 | Usually, however, the lock-out model implemented that way will perform |
|
|
1575 | miserably under the type of load it was designed to handle. In that case, |
|
|
1576 | it might be preferable to stop the real watcher before starting the |
|
|
1577 | idle watcher, so the kernel will not have to process the event in case |
|
|
1578 | the actual processing will be delayed for considerable time. |
|
|
1579 | |
|
|
1580 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1581 | priority than the default, and which should only process data when no |
|
|
1582 | other events are pending: |
|
|
1583 | |
|
|
1584 | ev_idle idle; // actual processing watcher |
|
|
1585 | ev_io io; // actual event watcher |
|
|
1586 | |
|
|
1587 | static void |
|
|
1588 | io_cb (EV_P_ ev_io *w, int revents) |
1096 | { |
1589 | { |
1097 | ev_io io; |
1590 | // stop the I/O watcher, we received the event, but |
1098 | int otherfd; |
1591 | // are not yet ready to handle it. |
1099 | void *somedata; |
1592 | ev_io_stop (EV_A_ w); |
1100 | struct whatever *mostinteresting; |
1593 | |
|
|
1594 | // start the idle watcher to handle the actual event. |
|
|
1595 | // it will not be executed as long as other watchers |
|
|
1596 | // with the default priority are receiving events. |
|
|
1597 | ev_idle_start (EV_A_ &idle); |
1101 | }; |
1598 | } |
1102 | |
1599 | |
1103 | ... |
1600 | static void |
1104 | struct my_io w; |
1601 | idle_cb (EV_P_ ev_idle *w, int revents) |
1105 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1106 | |
|
|
1107 | And since your callback will be called with a pointer to the watcher, you |
|
|
1108 | can cast it back to your own type: |
|
|
1109 | |
|
|
1110 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1111 | { |
1602 | { |
1112 | struct my_io *w = (struct my_io *)w_; |
1603 | // actual processing |
1113 | ... |
1604 | read (STDIN_FILENO, ...); |
|
|
1605 | |
|
|
1606 | // have to start the I/O watcher again, as |
|
|
1607 | // we have handled the event |
|
|
1608 | ev_io_start (EV_P_ &io); |
1114 | } |
1609 | } |
1115 | |
1610 | |
1116 | More interesting and less C-conformant ways of casting your callback type |
1611 | // initialisation |
1117 | instead have been omitted. |
1612 | ev_idle_init (&idle, idle_cb); |
|
|
1613 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1614 | ev_io_start (EV_DEFAULT_ &io); |
1118 | |
1615 | |
1119 | Another common scenario is to use some data structure with multiple |
1616 | In the "real" world, it might also be beneficial to start a timer, so that |
1120 | embedded watchers: |
1617 | low-priority connections can not be locked out forever under load. This |
1121 | |
1618 | enables your program to keep a lower latency for important connections |
1122 | struct my_biggy |
1619 | during short periods of high load, while not completely locking out less |
1123 | { |
1620 | important ones. |
1124 | int some_data; |
|
|
1125 | ev_timer t1; |
|
|
1126 | ev_timer t2; |
|
|
1127 | } |
|
|
1128 | |
|
|
1129 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1130 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1131 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1132 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1133 | programmers): |
|
|
1134 | |
|
|
1135 | #include <stddef.h> |
|
|
1136 | |
|
|
1137 | static void |
|
|
1138 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1139 | { |
|
|
1140 | struct my_biggy big = (struct my_biggy * |
|
|
1141 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1142 | } |
|
|
1143 | |
|
|
1144 | static void |
|
|
1145 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1146 | { |
|
|
1147 | struct my_biggy big = (struct my_biggy * |
|
|
1148 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1149 | } |
|
|
1150 | |
1621 | |
1151 | |
1622 | |
1152 | =head1 WATCHER TYPES |
1623 | =head1 WATCHER TYPES |
1153 | |
1624 | |
1154 | This section describes each watcher in detail, but will not repeat |
1625 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1178 | In general you can register as many read and/or write event watchers per |
1649 | In general you can register as many read and/or write event watchers per |
1179 | fd as you want (as long as you don't confuse yourself). Setting all file |
1650 | fd as you want (as long as you don't confuse yourself). Setting all file |
1180 | descriptors to non-blocking mode is also usually a good idea (but not |
1651 | descriptors to non-blocking mode is also usually a good idea (but not |
1181 | required if you know what you are doing). |
1652 | required if you know what you are doing). |
1182 | |
1653 | |
1183 | If you cannot use non-blocking mode, then force the use of a |
|
|
1184 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1185 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
|
|
1186 | |
|
|
1187 | Another thing you have to watch out for is that it is quite easy to |
1654 | Another thing you have to watch out for is that it is quite easy to |
1188 | receive "spurious" readiness notifications, that is your callback might |
1655 | receive "spurious" readiness notifications, that is, your callback might |
1189 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1656 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1190 | because there is no data. Not only are some backends known to create a |
1657 | because there is no data. It is very easy to get into this situation even |
1191 | lot of those (for example Solaris ports), it is very easy to get into |
1658 | with a relatively standard program structure. Thus it is best to always |
1192 | this situation even with a relatively standard program structure. Thus |
1659 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1193 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1194 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1660 | preferable to a program hanging until some data arrives. |
1195 | |
1661 | |
1196 | If you cannot run the fd in non-blocking mode (for example you should |
1662 | If you cannot run the fd in non-blocking mode (for example you should |
1197 | not play around with an Xlib connection), then you have to separately |
1663 | not play around with an Xlib connection), then you have to separately |
1198 | re-test whether a file descriptor is really ready with a known-to-be good |
1664 | re-test whether a file descriptor is really ready with a known-to-be good |
1199 | interface such as poll (fortunately in our Xlib example, Xlib already |
1665 | interface such as poll (fortunately in the case of Xlib, it already does |
1200 | does this on its own, so its quite safe to use). Some people additionally |
1666 | this on its own, so its quite safe to use). Some people additionally |
1201 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1667 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1202 | indefinitely. |
1668 | indefinitely. |
1203 | |
1669 | |
1204 | But really, best use non-blocking mode. |
1670 | But really, best use non-blocking mode. |
1205 | |
1671 | |
1206 | =head3 The special problem of disappearing file descriptors |
1672 | =head3 The special problem of disappearing file descriptors |
1207 | |
1673 | |
1208 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1674 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1209 | descriptor (either due to calling C<close> explicitly or any other means, |
1675 | a file descriptor (either due to calling C<close> explicitly or any other |
1210 | such as C<dup2>). The reason is that you register interest in some file |
1676 | means, such as C<dup2>). The reason is that you register interest in some |
1211 | descriptor, but when it goes away, the operating system will silently drop |
1677 | file descriptor, but when it goes away, the operating system will silently |
1212 | this interest. If another file descriptor with the same number then is |
1678 | drop this interest. If another file descriptor with the same number then |
1213 | registered with libev, there is no efficient way to see that this is, in |
1679 | is registered with libev, there is no efficient way to see that this is, |
1214 | fact, a different file descriptor. |
1680 | in fact, a different file descriptor. |
1215 | |
1681 | |
1216 | To avoid having to explicitly tell libev about such cases, libev follows |
1682 | To avoid having to explicitly tell libev about such cases, libev follows |
1217 | the following policy: Each time C<ev_io_set> is being called, libev |
1683 | the following policy: Each time C<ev_io_set> is being called, libev |
1218 | will assume that this is potentially a new file descriptor, otherwise |
1684 | will assume that this is potentially a new file descriptor, otherwise |
1219 | it is assumed that the file descriptor stays the same. That means that |
1685 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1233 | |
1699 | |
1234 | There is no workaround possible except not registering events |
1700 | There is no workaround possible except not registering events |
1235 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1701 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1236 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1702 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1237 | |
1703 | |
|
|
1704 | =head3 The special problem of files |
|
|
1705 | |
|
|
1706 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1707 | representing files, and expect it to become ready when their program |
|
|
1708 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1709 | |
|
|
1710 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1711 | notification as soon as the kernel knows whether and how much data is |
|
|
1712 | there, and in the case of open files, that's always the case, so you |
|
|
1713 | always get a readiness notification instantly, and your read (or possibly |
|
|
1714 | write) will still block on the disk I/O. |
|
|
1715 | |
|
|
1716 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1717 | devices and so on, there is another party (the sender) that delivers data |
|
|
1718 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1719 | will not send data on its own, simply because it doesn't know what you |
|
|
1720 | wish to read - you would first have to request some data. |
|
|
1721 | |
|
|
1722 | Since files are typically not-so-well supported by advanced notification |
|
|
1723 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1724 | to files, even though you should not use it. The reason for this is |
|
|
1725 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1726 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1727 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1728 | F</dev/urandom>), and even though the file might better be served with |
|
|
1729 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1730 | it "just works" instead of freezing. |
|
|
1731 | |
|
|
1732 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1733 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1734 | when you rarely read from a file instead of from a socket, and want to |
|
|
1735 | reuse the same code path. |
|
|
1736 | |
1238 | =head3 The special problem of fork |
1737 | =head3 The special problem of fork |
1239 | |
1738 | |
1240 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1739 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1241 | useless behaviour. Libev fully supports fork, but needs to be told about |
1740 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1242 | it in the child. |
1741 | to be told about it in the child if you want to continue to use it in the |
|
|
1742 | child. |
1243 | |
1743 | |
1244 | To support fork in your programs, you either have to call |
1744 | To support fork in your child processes, you have to call C<ev_loop_fork |
1245 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1745 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1246 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1746 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1247 | C<EVBACKEND_POLL>. |
|
|
1248 | |
1747 | |
1249 | =head3 The special problem of SIGPIPE |
1748 | =head3 The special problem of SIGPIPE |
1250 | |
1749 | |
1251 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1750 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1252 | when writing to a pipe whose other end has been closed, your program gets |
1751 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1255 | |
1754 | |
1256 | So when you encounter spurious, unexplained daemon exits, make sure you |
1755 | So when you encounter spurious, unexplained daemon exits, make sure you |
1257 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1756 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1258 | somewhere, as that would have given you a big clue). |
1757 | somewhere, as that would have given you a big clue). |
1259 | |
1758 | |
|
|
1759 | =head3 The special problem of accept()ing when you can't |
|
|
1760 | |
|
|
1761 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1762 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1763 | connection from the pending queue in all error cases. |
|
|
1764 | |
|
|
1765 | For example, larger servers often run out of file descriptors (because |
|
|
1766 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1767 | rejecting the connection, leading to libev signalling readiness on |
|
|
1768 | the next iteration again (the connection still exists after all), and |
|
|
1769 | typically causing the program to loop at 100% CPU usage. |
|
|
1770 | |
|
|
1771 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1772 | operating systems, there is usually little the app can do to remedy the |
|
|
1773 | situation, and no known thread-safe method of removing the connection to |
|
|
1774 | cope with overload is known (to me). |
|
|
1775 | |
|
|
1776 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1777 | - when the program encounters an overload, it will just loop until the |
|
|
1778 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1779 | event-based way to handle this situation, so it's the best one can do. |
|
|
1780 | |
|
|
1781 | A better way to handle the situation is to log any errors other than |
|
|
1782 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1783 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1784 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1785 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1786 | usage. |
|
|
1787 | |
|
|
1788 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1789 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1790 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1791 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1792 | clients under typical overload conditions. |
|
|
1793 | |
|
|
1794 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1795 | is often done with C<malloc> failures, but this results in an easy |
|
|
1796 | opportunity for a DoS attack. |
1260 | |
1797 | |
1261 | =head3 Watcher-Specific Functions |
1798 | =head3 Watcher-Specific Functions |
1262 | |
1799 | |
1263 | =over 4 |
1800 | =over 4 |
1264 | |
1801 | |
… | |
… | |
1296 | ... |
1833 | ... |
1297 | struct ev_loop *loop = ev_default_init (0); |
1834 | struct ev_loop *loop = ev_default_init (0); |
1298 | ev_io stdin_readable; |
1835 | ev_io stdin_readable; |
1299 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1836 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1300 | ev_io_start (loop, &stdin_readable); |
1837 | ev_io_start (loop, &stdin_readable); |
1301 | ev_loop (loop, 0); |
1838 | ev_run (loop, 0); |
1302 | |
1839 | |
1303 | |
1840 | |
1304 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1841 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1305 | |
1842 | |
1306 | Timer watchers are simple relative timers that generate an event after a |
1843 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1311 | year, it will still time out after (roughly) one hour. "Roughly" because |
1848 | year, it will still time out after (roughly) one hour. "Roughly" because |
1312 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1849 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1313 | monotonic clock option helps a lot here). |
1850 | monotonic clock option helps a lot here). |
1314 | |
1851 | |
1315 | The callback is guaranteed to be invoked only I<after> its timeout has |
1852 | The callback is guaranteed to be invoked only I<after> its timeout has |
1316 | passed, but if multiple timers become ready during the same loop iteration |
1853 | passed (not I<at>, so on systems with very low-resolution clocks this |
1317 | then order of execution is undefined. |
1854 | might introduce a small delay, see "the special problem of being too |
|
|
1855 | early", below). If multiple timers become ready during the same loop |
|
|
1856 | iteration then the ones with earlier time-out values are invoked before |
|
|
1857 | ones of the same priority with later time-out values (but this is no |
|
|
1858 | longer true when a callback calls C<ev_run> recursively). |
1318 | |
1859 | |
1319 | =head3 Be smart about timeouts |
1860 | =head3 Be smart about timeouts |
1320 | |
1861 | |
1321 | Many real-world problems involve some kind of timeout, usually for error |
1862 | Many real-world problems involve some kind of timeout, usually for error |
1322 | recovery. A typical example is an HTTP request - if the other side hangs, |
1863 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1366 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1907 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1367 | member and C<ev_timer_again>. |
1908 | member and C<ev_timer_again>. |
1368 | |
1909 | |
1369 | At start: |
1910 | At start: |
1370 | |
1911 | |
1371 | ev_timer_init (timer, callback); |
1912 | ev_init (timer, callback); |
1372 | timer->repeat = 60.; |
1913 | timer->repeat = 60.; |
1373 | ev_timer_again (loop, timer); |
1914 | ev_timer_again (loop, timer); |
1374 | |
1915 | |
1375 | Each time there is some activity: |
1916 | Each time there is some activity: |
1376 | |
1917 | |
… | |
… | |
1397 | |
1938 | |
1398 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1939 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1399 | but remember the time of last activity, and check for a real timeout only |
1940 | but remember the time of last activity, and check for a real timeout only |
1400 | within the callback: |
1941 | within the callback: |
1401 | |
1942 | |
|
|
1943 | ev_tstamp timeout = 60.; |
1402 | ev_tstamp last_activity; // time of last activity |
1944 | ev_tstamp last_activity; // time of last activity |
|
|
1945 | ev_timer timer; |
1403 | |
1946 | |
1404 | static void |
1947 | static void |
1405 | callback (EV_P_ ev_timer *w, int revents) |
1948 | callback (EV_P_ ev_timer *w, int revents) |
1406 | { |
1949 | { |
1407 | ev_tstamp now = ev_now (EV_A); |
1950 | // calculate when the timeout would happen |
1408 | ev_tstamp timeout = last_activity + 60.; |
1951 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1409 | |
1952 | |
1410 | // if last_activity + 60. is older than now, we did time out |
1953 | // if negative, it means we the timeout already occurred |
1411 | if (timeout < now) |
1954 | if (after < 0.) |
1412 | { |
1955 | { |
1413 | // timeout occured, take action |
1956 | // timeout occurred, take action |
1414 | } |
1957 | } |
1415 | else |
1958 | else |
1416 | { |
1959 | { |
1417 | // callback was invoked, but there was some activity, re-arm |
1960 | // callback was invoked, but there was some recent |
1418 | // the watcher to fire in last_activity + 60, which is |
1961 | // activity. simply restart the timer to time out |
1419 | // guaranteed to be in the future, so "again" is positive: |
1962 | // after "after" seconds, which is the earliest time |
1420 | w->again = timeout - now; |
1963 | // the timeout can occur. |
|
|
1964 | ev_timer_set (w, after, 0.); |
1421 | ev_timer_again (EV_A_ w); |
1965 | ev_timer_start (EV_A_ w); |
1422 | } |
1966 | } |
1423 | } |
1967 | } |
1424 | |
1968 | |
1425 | To summarise the callback: first calculate the real timeout (defined |
1969 | To summarise the callback: first calculate in how many seconds the |
1426 | as "60 seconds after the last activity"), then check if that time has |
1970 | timeout will occur (by calculating the absolute time when it would occur, |
1427 | been reached, which means something I<did>, in fact, time out. Otherwise |
1971 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1428 | the callback was invoked too early (C<timeout> is in the future), so |
1972 | (EV_A)> from that). |
1429 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1430 | a timeout then. |
|
|
1431 | |
1973 | |
1432 | Note how C<ev_timer_again> is used, taking advantage of the |
1974 | If this value is negative, then we are already past the timeout, i.e. we |
1433 | C<ev_timer_again> optimisation when the timer is already running. |
1975 | timed out, and need to do whatever is needed in this case. |
|
|
1976 | |
|
|
1977 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1978 | and simply start the timer with this timeout value. |
|
|
1979 | |
|
|
1980 | In other words, each time the callback is invoked it will check whether |
|
|
1981 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1982 | again at the earliest time it could time out. Rinse. Repeat. |
1434 | |
1983 | |
1435 | This scheme causes more callback invocations (about one every 60 seconds |
1984 | This scheme causes more callback invocations (about one every 60 seconds |
1436 | minus half the average time between activity), but virtually no calls to |
1985 | minus half the average time between activity), but virtually no calls to |
1437 | libev to change the timeout. |
1986 | libev to change the timeout. |
1438 | |
1987 | |
1439 | To start the timer, simply initialise the watcher and set C<last_activity> |
1988 | To start the machinery, simply initialise the watcher and set |
1440 | to the current time (meaning we just have some activity :), then call the |
1989 | C<last_activity> to the current time (meaning there was some activity just |
1441 | callback, which will "do the right thing" and start the timer: |
1990 | now), then call the callback, which will "do the right thing" and start |
|
|
1991 | the timer: |
1442 | |
1992 | |
|
|
1993 | last_activity = ev_now (EV_A); |
1443 | ev_timer_init (timer, callback); |
1994 | ev_init (&timer, callback); |
1444 | last_activity = ev_now (loop); |
1995 | callback (EV_A_ &timer, 0); |
1445 | callback (loop, timer, EV_TIMEOUT); |
|
|
1446 | |
1996 | |
1447 | And when there is some activity, simply store the current time in |
1997 | When there is some activity, simply store the current time in |
1448 | C<last_activity>, no libev calls at all: |
1998 | C<last_activity>, no libev calls at all: |
1449 | |
1999 | |
|
|
2000 | if (activity detected) |
1450 | last_actiivty = ev_now (loop); |
2001 | last_activity = ev_now (EV_A); |
|
|
2002 | |
|
|
2003 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2004 | providing a new value, stopping the timer and calling the callback, which |
|
|
2005 | will again do the right thing (for example, time out immediately :). |
|
|
2006 | |
|
|
2007 | timeout = new_value; |
|
|
2008 | ev_timer_stop (EV_A_ &timer); |
|
|
2009 | callback (EV_A_ &timer, 0); |
1451 | |
2010 | |
1452 | This technique is slightly more complex, but in most cases where the |
2011 | This technique is slightly more complex, but in most cases where the |
1453 | time-out is unlikely to be triggered, much more efficient. |
2012 | time-out is unlikely to be triggered, much more efficient. |
1454 | |
|
|
1455 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1456 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1457 | fix things for you. |
|
|
1458 | |
2013 | |
1459 | =item 4. Wee, just use a double-linked list for your timeouts. |
2014 | =item 4. Wee, just use a double-linked list for your timeouts. |
1460 | |
2015 | |
1461 | If there is not one request, but many thousands (millions...), all |
2016 | If there is not one request, but many thousands (millions...), all |
1462 | employing some kind of timeout with the same timeout value, then one can |
2017 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1489 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2044 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1490 | rather complicated, but extremely efficient, something that really pays |
2045 | rather complicated, but extremely efficient, something that really pays |
1491 | off after the first million or so of active timers, i.e. it's usually |
2046 | off after the first million or so of active timers, i.e. it's usually |
1492 | overkill :) |
2047 | overkill :) |
1493 | |
2048 | |
|
|
2049 | =head3 The special problem of being too early |
|
|
2050 | |
|
|
2051 | If you ask a timer to call your callback after three seconds, then |
|
|
2052 | you expect it to be invoked after three seconds - but of course, this |
|
|
2053 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2054 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2055 | process with a STOP signal for a few hours for example. |
|
|
2056 | |
|
|
2057 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2058 | delay has occurred, but cannot guarantee this. |
|
|
2059 | |
|
|
2060 | A less obvious failure mode is calling your callback too early: many event |
|
|
2061 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2062 | this can cause your callback to be invoked much earlier than you would |
|
|
2063 | expect. |
|
|
2064 | |
|
|
2065 | To see why, imagine a system with a clock that only offers full second |
|
|
2066 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2067 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2068 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2069 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2070 | |
|
|
2071 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2072 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2073 | one-second delay was requested - this is being "too early", despite best |
|
|
2074 | intentions. |
|
|
2075 | |
|
|
2076 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2077 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2078 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2079 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2080 | |
|
|
2081 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2082 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2083 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2084 | late" side of things. |
|
|
2085 | |
1494 | =head3 The special problem of time updates |
2086 | =head3 The special problem of time updates |
1495 | |
2087 | |
1496 | Establishing the current time is a costly operation (it usually takes at |
2088 | Establishing the current time is a costly operation (it usually takes |
1497 | least two system calls): EV therefore updates its idea of the current |
2089 | at least one system call): EV therefore updates its idea of the current |
1498 | time only before and after C<ev_loop> collects new events, which causes a |
2090 | time only before and after C<ev_run> collects new events, which causes a |
1499 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2091 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1500 | lots of events in one iteration. |
2092 | lots of events in one iteration. |
1501 | |
2093 | |
1502 | The relative timeouts are calculated relative to the C<ev_now ()> |
2094 | The relative timeouts are calculated relative to the C<ev_now ()> |
1503 | time. This is usually the right thing as this timestamp refers to the time |
2095 | time. This is usually the right thing as this timestamp refers to the time |
1504 | of the event triggering whatever timeout you are modifying/starting. If |
2096 | of the event triggering whatever timeout you are modifying/starting. If |
1505 | you suspect event processing to be delayed and you I<need> to base the |
2097 | you suspect event processing to be delayed and you I<need> to base the |
1506 | timeout on the current time, use something like this to adjust for this: |
2098 | timeout on the current time, use something like the following to adjust |
|
|
2099 | for it: |
1507 | |
2100 | |
1508 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2101 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1509 | |
2102 | |
1510 | If the event loop is suspended for a long time, you can also force an |
2103 | If the event loop is suspended for a long time, you can also force an |
1511 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2104 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1512 | ()>. |
2105 | ()>, although that will push the event time of all outstanding events |
|
|
2106 | further into the future. |
|
|
2107 | |
|
|
2108 | =head3 The special problem of unsynchronised clocks |
|
|
2109 | |
|
|
2110 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2111 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2112 | jumps). |
|
|
2113 | |
|
|
2114 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2115 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2116 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2117 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2118 | than a directly following call to C<time>. |
|
|
2119 | |
|
|
2120 | The moral of this is to only compare libev-related timestamps with |
|
|
2121 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2122 | a second or so. |
|
|
2123 | |
|
|
2124 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2125 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2126 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2127 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2128 | |
|
|
2129 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2130 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2131 | I<measured according to the real time>, not the system clock. |
|
|
2132 | |
|
|
2133 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2134 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2135 | exactly the right behaviour. |
|
|
2136 | |
|
|
2137 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2138 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2139 | time, where your comparisons will always generate correct results. |
|
|
2140 | |
|
|
2141 | =head3 The special problems of suspended animation |
|
|
2142 | |
|
|
2143 | When you leave the server world it is quite customary to hit machines that |
|
|
2144 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2145 | |
|
|
2146 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2147 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2148 | to run until the system is suspended, but they will not advance while the |
|
|
2149 | system is suspended. That means, on resume, it will be as if the program |
|
|
2150 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2151 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2152 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2153 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2154 | be adjusted accordingly. |
|
|
2155 | |
|
|
2156 | I would not be surprised to see different behaviour in different between |
|
|
2157 | operating systems, OS versions or even different hardware. |
|
|
2158 | |
|
|
2159 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2160 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2161 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2162 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2163 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2164 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2165 | |
|
|
2166 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2167 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2168 | deterministic behaviour in this case (you can do nothing against |
|
|
2169 | C<SIGSTOP>). |
1513 | |
2170 | |
1514 | =head3 Watcher-Specific Functions and Data Members |
2171 | =head3 Watcher-Specific Functions and Data Members |
1515 | |
2172 | |
1516 | =over 4 |
2173 | =over 4 |
1517 | |
2174 | |
1518 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2175 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1519 | |
2176 | |
1520 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2177 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1521 | |
2178 | |
1522 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2179 | Configure the timer to trigger after C<after> seconds (fractional and |
1523 | is C<0.>, then it will automatically be stopped once the timeout is |
2180 | negative values are supported). If C<repeat> is C<0.>, then it will |
1524 | reached. If it is positive, then the timer will automatically be |
2181 | automatically be stopped once the timeout is reached. If it is positive, |
1525 | configured to trigger again C<repeat> seconds later, again, and again, |
2182 | then the timer will automatically be configured to trigger again C<repeat> |
1526 | until stopped manually. |
2183 | seconds later, again, and again, until stopped manually. |
1527 | |
2184 | |
1528 | The timer itself will do a best-effort at avoiding drift, that is, if |
2185 | The timer itself will do a best-effort at avoiding drift, that is, if |
1529 | you configure a timer to trigger every 10 seconds, then it will normally |
2186 | you configure a timer to trigger every 10 seconds, then it will normally |
1530 | trigger at exactly 10 second intervals. If, however, your program cannot |
2187 | trigger at exactly 10 second intervals. If, however, your program cannot |
1531 | keep up with the timer (because it takes longer than those 10 seconds to |
2188 | keep up with the timer (because it takes longer than those 10 seconds to |
1532 | do stuff) the timer will not fire more than once per event loop iteration. |
2189 | do stuff) the timer will not fire more than once per event loop iteration. |
1533 | |
2190 | |
1534 | =item ev_timer_again (loop, ev_timer *) |
2191 | =item ev_timer_again (loop, ev_timer *) |
1535 | |
2192 | |
1536 | This will act as if the timer timed out and restart it again if it is |
2193 | This will act as if the timer timed out, and restarts it again if it is |
1537 | repeating. The exact semantics are: |
2194 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2195 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1538 | |
2196 | |
|
|
2197 | The exact semantics are as in the following rules, all of which will be |
|
|
2198 | applied to the watcher: |
|
|
2199 | |
|
|
2200 | =over 4 |
|
|
2201 | |
1539 | If the timer is pending, its pending status is cleared. |
2202 | =item If the timer is pending, the pending status is always cleared. |
1540 | |
2203 | |
1541 | If the timer is started but non-repeating, stop it (as if it timed out). |
2204 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2205 | out, without invoking it). |
1542 | |
2206 | |
1543 | If the timer is repeating, either start it if necessary (with the |
2207 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1544 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2208 | and start the timer, if necessary. |
1545 | |
2209 | |
|
|
2210 | =back |
|
|
2211 | |
1546 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
2212 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1547 | usage example. |
2213 | usage example. |
|
|
2214 | |
|
|
2215 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
2216 | |
|
|
2217 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
2218 | then this time is relative to the current event loop time, otherwise it's |
|
|
2219 | the timeout value currently configured. |
|
|
2220 | |
|
|
2221 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2222 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2223 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2224 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2225 | too), and so on. |
1548 | |
2226 | |
1549 | =item ev_tstamp repeat [read-write] |
2227 | =item ev_tstamp repeat [read-write] |
1550 | |
2228 | |
1551 | The current C<repeat> value. Will be used each time the watcher times out |
2229 | The current C<repeat> value. Will be used each time the watcher times out |
1552 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2230 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1578 | } |
2256 | } |
1579 | |
2257 | |
1580 | ev_timer mytimer; |
2258 | ev_timer mytimer; |
1581 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2259 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1582 | ev_timer_again (&mytimer); /* start timer */ |
2260 | ev_timer_again (&mytimer); /* start timer */ |
1583 | ev_loop (loop, 0); |
2261 | ev_run (loop, 0); |
1584 | |
2262 | |
1585 | // and in some piece of code that gets executed on any "activity": |
2263 | // and in some piece of code that gets executed on any "activity": |
1586 | // reset the timeout to start ticking again at 10 seconds |
2264 | // reset the timeout to start ticking again at 10 seconds |
1587 | ev_timer_again (&mytimer); |
2265 | ev_timer_again (&mytimer); |
1588 | |
2266 | |
… | |
… | |
1590 | =head2 C<ev_periodic> - to cron or not to cron? |
2268 | =head2 C<ev_periodic> - to cron or not to cron? |
1591 | |
2269 | |
1592 | Periodic watchers are also timers of a kind, but they are very versatile |
2270 | Periodic watchers are also timers of a kind, but they are very versatile |
1593 | (and unfortunately a bit complex). |
2271 | (and unfortunately a bit complex). |
1594 | |
2272 | |
1595 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2273 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1596 | but on wall clock time (absolute time). You can tell a periodic watcher |
2274 | relative time, the physical time that passes) but on wall clock time |
1597 | to trigger after some specific point in time. For example, if you tell a |
2275 | (absolute time, the thing you can read on your calendar or clock). The |
1598 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2276 | difference is that wall clock time can run faster or slower than real |
1599 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2277 | time, and time jumps are not uncommon (e.g. when you adjust your |
1600 | clock to January of the previous year, then it will take more than year |
2278 | wrist-watch). |
1601 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1602 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1603 | |
2279 | |
|
|
2280 | You can tell a periodic watcher to trigger after some specific point |
|
|
2281 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2282 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2283 | not a delay) and then reset your system clock to January of the previous |
|
|
2284 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2285 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2286 | it, as it uses a relative timeout). |
|
|
2287 | |
1604 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2288 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1605 | such as triggering an event on each "midnight, local time", or other |
2289 | timers, such as triggering an event on each "midnight, local time", or |
1606 | complicated rules. |
2290 | other complicated rules. This cannot easily be done with C<ev_timer> |
|
|
2291 | watchers, as those cannot react to time jumps. |
1607 | |
2292 | |
1608 | As with timers, the callback is guaranteed to be invoked only when the |
2293 | As with timers, the callback is guaranteed to be invoked only when the |
1609 | time (C<at>) has passed, but if multiple periodic timers become ready |
2294 | point in time where it is supposed to trigger has passed. If multiple |
1610 | during the same loop iteration, then order of execution is undefined. |
2295 | timers become ready during the same loop iteration then the ones with |
|
|
2296 | earlier time-out values are invoked before ones with later time-out values |
|
|
2297 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1611 | |
2298 | |
1612 | =head3 Watcher-Specific Functions and Data Members |
2299 | =head3 Watcher-Specific Functions and Data Members |
1613 | |
2300 | |
1614 | =over 4 |
2301 | =over 4 |
1615 | |
2302 | |
1616 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2303 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1617 | |
2304 | |
1618 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2305 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1619 | |
2306 | |
1620 | Lots of arguments, lets sort it out... There are basically three modes of |
2307 | Lots of arguments, let's sort it out... There are basically three modes of |
1621 | operation, and we will explain them from simplest to most complex: |
2308 | operation, and we will explain them from simplest to most complex: |
1622 | |
2309 | |
1623 | =over 4 |
2310 | =over 4 |
1624 | |
2311 | |
1625 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2312 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1626 | |
2313 | |
1627 | In this configuration the watcher triggers an event after the wall clock |
2314 | In this configuration the watcher triggers an event after the wall clock |
1628 | time C<at> has passed. It will not repeat and will not adjust when a time |
2315 | time C<offset> has passed. It will not repeat and will not adjust when a |
1629 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2316 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1630 | only run when the system clock reaches or surpasses this time. |
2317 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2318 | this point in time. |
1631 | |
2319 | |
1632 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2320 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1633 | |
2321 | |
1634 | In this mode the watcher will always be scheduled to time out at the next |
2322 | In this mode the watcher will always be scheduled to time out at the next |
1635 | C<at + N * interval> time (for some integer N, which can also be negative) |
2323 | C<offset + N * interval> time (for some integer N, which can also be |
1636 | and then repeat, regardless of any time jumps. |
2324 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2325 | argument is merely an offset into the C<interval> periods. |
1637 | |
2326 | |
1638 | This can be used to create timers that do not drift with respect to the |
2327 | This can be used to create timers that do not drift with respect to the |
1639 | system clock, for example, here is a C<ev_periodic> that triggers each |
2328 | system clock, for example, here is an C<ev_periodic> that triggers each |
1640 | hour, on the hour: |
2329 | hour, on the hour (with respect to UTC): |
1641 | |
2330 | |
1642 | ev_periodic_set (&periodic, 0., 3600., 0); |
2331 | ev_periodic_set (&periodic, 0., 3600., 0); |
1643 | |
2332 | |
1644 | This doesn't mean there will always be 3600 seconds in between triggers, |
2333 | This doesn't mean there will always be 3600 seconds in between triggers, |
1645 | but only that the callback will be called when the system time shows a |
2334 | but only that the callback will be called when the system time shows a |
1646 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2335 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1647 | by 3600. |
2336 | by 3600. |
1648 | |
2337 | |
1649 | Another way to think about it (for the mathematically inclined) is that |
2338 | Another way to think about it (for the mathematically inclined) is that |
1650 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2339 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1651 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2340 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1652 | |
2341 | |
1653 | For numerical stability it is preferable that the C<at> value is near |
2342 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1654 | C<ev_now ()> (the current time), but there is no range requirement for |
2343 | interval value should be higher than C<1/8192> (which is around 100 |
1655 | this value, and in fact is often specified as zero. |
2344 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2345 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2346 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2347 | C<0> and C<interval>, which is also the recommended range. |
1656 | |
2348 | |
1657 | Note also that there is an upper limit to how often a timer can fire (CPU |
2349 | Note also that there is an upper limit to how often a timer can fire (CPU |
1658 | speed for example), so if C<interval> is very small then timing stability |
2350 | speed for example), so if C<interval> is very small then timing stability |
1659 | will of course deteriorate. Libev itself tries to be exact to be about one |
2351 | will of course deteriorate. Libev itself tries to be exact to be about one |
1660 | millisecond (if the OS supports it and the machine is fast enough). |
2352 | millisecond (if the OS supports it and the machine is fast enough). |
1661 | |
2353 | |
1662 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2354 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1663 | |
2355 | |
1664 | In this mode the values for C<interval> and C<at> are both being |
2356 | In this mode the values for C<interval> and C<offset> are both being |
1665 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2357 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1666 | reschedule callback will be called with the watcher as first, and the |
2358 | reschedule callback will be called with the watcher as first, and the |
1667 | current time as second argument. |
2359 | current time as second argument. |
1668 | |
2360 | |
1669 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2361 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1670 | ever, or make ANY event loop modifications whatsoever>. |
2362 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2363 | allowed by documentation here>. |
1671 | |
2364 | |
1672 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2365 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1673 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2366 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1674 | only event loop modification you are allowed to do). |
2367 | only event loop modification you are allowed to do). |
1675 | |
2368 | |
… | |
… | |
1689 | |
2382 | |
1690 | NOTE: I<< This callback must always return a time that is higher than or |
2383 | NOTE: I<< This callback must always return a time that is higher than or |
1691 | equal to the passed C<now> value >>. |
2384 | equal to the passed C<now> value >>. |
1692 | |
2385 | |
1693 | This can be used to create very complex timers, such as a timer that |
2386 | This can be used to create very complex timers, such as a timer that |
1694 | triggers on "next midnight, local time". To do this, you would calculate the |
2387 | triggers on "next midnight, local time". To do this, you would calculate |
1695 | next midnight after C<now> and return the timestamp value for this. How |
2388 | the next midnight after C<now> and return the timestamp value for |
1696 | you do this is, again, up to you (but it is not trivial, which is the main |
2389 | this. Here is a (completely untested, no error checking) example on how to |
1697 | reason I omitted it as an example). |
2390 | do this: |
|
|
2391 | |
|
|
2392 | #include <time.h> |
|
|
2393 | |
|
|
2394 | static ev_tstamp |
|
|
2395 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2396 | { |
|
|
2397 | time_t tnow = (time_t)now; |
|
|
2398 | struct tm tm; |
|
|
2399 | localtime_r (&tnow, &tm); |
|
|
2400 | |
|
|
2401 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2402 | ++tm.tm_mday; // midnight next day |
|
|
2403 | |
|
|
2404 | return mktime (&tm); |
|
|
2405 | } |
|
|
2406 | |
|
|
2407 | Note: this code might run into trouble on days that have more then two |
|
|
2408 | midnights (beginning and end). |
1698 | |
2409 | |
1699 | =back |
2410 | =back |
1700 | |
2411 | |
1701 | =item ev_periodic_again (loop, ev_periodic *) |
2412 | =item ev_periodic_again (loop, ev_periodic *) |
1702 | |
2413 | |
… | |
… | |
1705 | a different time than the last time it was called (e.g. in a crond like |
2416 | a different time than the last time it was called (e.g. in a crond like |
1706 | program when the crontabs have changed). |
2417 | program when the crontabs have changed). |
1707 | |
2418 | |
1708 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2419 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1709 | |
2420 | |
1710 | When active, returns the absolute time that the watcher is supposed to |
2421 | When active, returns the absolute time that the watcher is supposed |
1711 | trigger next. |
2422 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2423 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2424 | rescheduling modes. |
1712 | |
2425 | |
1713 | =item ev_tstamp offset [read-write] |
2426 | =item ev_tstamp offset [read-write] |
1714 | |
2427 | |
1715 | When repeating, this contains the offset value, otherwise this is the |
2428 | When repeating, this contains the offset value, otherwise this is the |
1716 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2429 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2430 | although libev might modify this value for better numerical stability). |
1717 | |
2431 | |
1718 | Can be modified any time, but changes only take effect when the periodic |
2432 | Can be modified any time, but changes only take effect when the periodic |
1719 | timer fires or C<ev_periodic_again> is being called. |
2433 | timer fires or C<ev_periodic_again> is being called. |
1720 | |
2434 | |
1721 | =item ev_tstamp interval [read-write] |
2435 | =item ev_tstamp interval [read-write] |
… | |
… | |
1737 | Example: Call a callback every hour, or, more precisely, whenever the |
2451 | Example: Call a callback every hour, or, more precisely, whenever the |
1738 | system time is divisible by 3600. The callback invocation times have |
2452 | system time is divisible by 3600. The callback invocation times have |
1739 | potentially a lot of jitter, but good long-term stability. |
2453 | potentially a lot of jitter, but good long-term stability. |
1740 | |
2454 | |
1741 | static void |
2455 | static void |
1742 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2456 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1743 | { |
2457 | { |
1744 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2458 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1745 | } |
2459 | } |
1746 | |
2460 | |
1747 | ev_periodic hourly_tick; |
2461 | ev_periodic hourly_tick; |
… | |
… | |
1764 | |
2478 | |
1765 | ev_periodic hourly_tick; |
2479 | ev_periodic hourly_tick; |
1766 | ev_periodic_init (&hourly_tick, clock_cb, |
2480 | ev_periodic_init (&hourly_tick, clock_cb, |
1767 | fmod (ev_now (loop), 3600.), 3600., 0); |
2481 | fmod (ev_now (loop), 3600.), 3600., 0); |
1768 | ev_periodic_start (loop, &hourly_tick); |
2482 | ev_periodic_start (loop, &hourly_tick); |
1769 | |
2483 | |
1770 | |
2484 | |
1771 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2485 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1772 | |
2486 | |
1773 | Signal watchers will trigger an event when the process receives a specific |
2487 | Signal watchers will trigger an event when the process receives a specific |
1774 | signal one or more times. Even though signals are very asynchronous, libev |
2488 | signal one or more times. Even though signals are very asynchronous, libev |
1775 | will try it's best to deliver signals synchronously, i.e. as part of the |
2489 | will try its best to deliver signals synchronously, i.e. as part of the |
1776 | normal event processing, like any other event. |
2490 | normal event processing, like any other event. |
1777 | |
2491 | |
1778 | If you want signals asynchronously, just use C<sigaction> as you would |
2492 | If you want signals to be delivered truly asynchronously, just use |
1779 | do without libev and forget about sharing the signal. You can even use |
2493 | C<sigaction> as you would do without libev and forget about sharing |
1780 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2494 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2495 | synchronously wake up an event loop. |
1781 | |
2496 | |
1782 | You can configure as many watchers as you like per signal. Only when the |
2497 | You can configure as many watchers as you like for the same signal, but |
1783 | first watcher gets started will libev actually register a signal handler |
2498 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
1784 | with the kernel (thus it coexists with your own signal handlers as long as |
2499 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
1785 | you don't register any with libev for the same signal). Similarly, when |
2500 | C<SIGINT> in both the default loop and another loop at the same time. At |
1786 | the last signal watcher for a signal is stopped, libev will reset the |
2501 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
1787 | signal handler to SIG_DFL (regardless of what it was set to before). |
2502 | |
|
|
2503 | Only after the first watcher for a signal is started will libev actually |
|
|
2504 | register something with the kernel. It thus coexists with your own signal |
|
|
2505 | handlers as long as you don't register any with libev for the same signal. |
1788 | |
2506 | |
1789 | If possible and supported, libev will install its handlers with |
2507 | If possible and supported, libev will install its handlers with |
1790 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2508 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1791 | interrupted. If you have a problem with system calls getting interrupted by |
2509 | not be unduly interrupted. If you have a problem with system calls getting |
1792 | signals you can block all signals in an C<ev_check> watcher and unblock |
2510 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1793 | them in an C<ev_prepare> watcher. |
2511 | and unblock them in an C<ev_prepare> watcher. |
|
|
2512 | |
|
|
2513 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2514 | |
|
|
2515 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2516 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2517 | stopping it again), that is, libev might or might not block the signal, |
|
|
2518 | and might or might not set or restore the installed signal handler (but |
|
|
2519 | see C<EVFLAG_NOSIGMASK>). |
|
|
2520 | |
|
|
2521 | While this does not matter for the signal disposition (libev never |
|
|
2522 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2523 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2524 | certain signals to be blocked. |
|
|
2525 | |
|
|
2526 | This means that before calling C<exec> (from the child) you should reset |
|
|
2527 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2528 | choice usually). |
|
|
2529 | |
|
|
2530 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2531 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2532 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2533 | |
|
|
2534 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2535 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2536 | the window of opportunity for problems, it will not go away, as libev |
|
|
2537 | I<has> to modify the signal mask, at least temporarily. |
|
|
2538 | |
|
|
2539 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2540 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2541 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2542 | |
|
|
2543 | =head3 The special problem of threads signal handling |
|
|
2544 | |
|
|
2545 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2546 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2547 | threads in a process block signals, which is hard to achieve. |
|
|
2548 | |
|
|
2549 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2550 | for the same signals), you can tackle this problem by globally blocking |
|
|
2551 | all signals before creating any threads (or creating them with a fully set |
|
|
2552 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2553 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2554 | these signals. You can pass on any signals that libev might be interested |
|
|
2555 | in by calling C<ev_feed_signal>. |
1794 | |
2556 | |
1795 | =head3 Watcher-Specific Functions and Data Members |
2557 | =head3 Watcher-Specific Functions and Data Members |
1796 | |
2558 | |
1797 | =over 4 |
2559 | =over 4 |
1798 | |
2560 | |
… | |
… | |
1814 | Example: Try to exit cleanly on SIGINT. |
2576 | Example: Try to exit cleanly on SIGINT. |
1815 | |
2577 | |
1816 | static void |
2578 | static void |
1817 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2579 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1818 | { |
2580 | { |
1819 | ev_unloop (loop, EVUNLOOP_ALL); |
2581 | ev_break (loop, EVBREAK_ALL); |
1820 | } |
2582 | } |
1821 | |
2583 | |
1822 | ev_signal signal_watcher; |
2584 | ev_signal signal_watcher; |
1823 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2585 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1824 | ev_signal_start (loop, &signal_watcher); |
2586 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
1830 | some child status changes (most typically when a child of yours dies or |
2592 | some child status changes (most typically when a child of yours dies or |
1831 | exits). It is permissible to install a child watcher I<after> the child |
2593 | exits). It is permissible to install a child watcher I<after> the child |
1832 | has been forked (which implies it might have already exited), as long |
2594 | has been forked (which implies it might have already exited), as long |
1833 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2595 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1834 | forking and then immediately registering a watcher for the child is fine, |
2596 | forking and then immediately registering a watcher for the child is fine, |
1835 | but forking and registering a watcher a few event loop iterations later is |
2597 | but forking and registering a watcher a few event loop iterations later or |
1836 | not. |
2598 | in the next callback invocation is not. |
1837 | |
2599 | |
1838 | Only the default event loop is capable of handling signals, and therefore |
2600 | Only the default event loop is capable of handling signals, and therefore |
1839 | you can only register child watchers in the default event loop. |
2601 | you can only register child watchers in the default event loop. |
1840 | |
2602 | |
|
|
2603 | Due to some design glitches inside libev, child watchers will always be |
|
|
2604 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2605 | libev) |
|
|
2606 | |
1841 | =head3 Process Interaction |
2607 | =head3 Process Interaction |
1842 | |
2608 | |
1843 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2609 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1844 | initialised. This is necessary to guarantee proper behaviour even if |
2610 | initialised. This is necessary to guarantee proper behaviour even if the |
1845 | the first child watcher is started after the child exits. The occurrence |
2611 | first child watcher is started after the child exits. The occurrence |
1846 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2612 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1847 | synchronously as part of the event loop processing. Libev always reaps all |
2613 | synchronously as part of the event loop processing. Libev always reaps all |
1848 | children, even ones not watched. |
2614 | children, even ones not watched. |
1849 | |
2615 | |
1850 | =head3 Overriding the Built-In Processing |
2616 | =head3 Overriding the Built-In Processing |
… | |
… | |
1860 | =head3 Stopping the Child Watcher |
2626 | =head3 Stopping the Child Watcher |
1861 | |
2627 | |
1862 | Currently, the child watcher never gets stopped, even when the |
2628 | Currently, the child watcher never gets stopped, even when the |
1863 | child terminates, so normally one needs to stop the watcher in the |
2629 | child terminates, so normally one needs to stop the watcher in the |
1864 | callback. Future versions of libev might stop the watcher automatically |
2630 | callback. Future versions of libev might stop the watcher automatically |
1865 | when a child exit is detected. |
2631 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2632 | problem). |
1866 | |
2633 | |
1867 | =head3 Watcher-Specific Functions and Data Members |
2634 | =head3 Watcher-Specific Functions and Data Members |
1868 | |
2635 | |
1869 | =over 4 |
2636 | =over 4 |
1870 | |
2637 | |
… | |
… | |
1928 | |
2695 | |
1929 | =head2 C<ev_stat> - did the file attributes just change? |
2696 | =head2 C<ev_stat> - did the file attributes just change? |
1930 | |
2697 | |
1931 | This watches a file system path for attribute changes. That is, it calls |
2698 | This watches a file system path for attribute changes. That is, it calls |
1932 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2699 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1933 | and sees if it changed compared to the last time, invoking the callback if |
2700 | and sees if it changed compared to the last time, invoking the callback |
1934 | it did. |
2701 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2702 | happen after the watcher has been started will be reported. |
1935 | |
2703 | |
1936 | The path does not need to exist: changing from "path exists" to "path does |
2704 | The path does not need to exist: changing from "path exists" to "path does |
1937 | not exist" is a status change like any other. The condition "path does not |
2705 | not exist" is a status change like any other. The condition "path does not |
1938 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2706 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1939 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2707 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2006 | the process. The exception are C<ev_stat> watchers - those call C<stat |
2774 | the process. The exception are C<ev_stat> watchers - those call C<stat |
2007 | ()>, which is a synchronous operation. |
2775 | ()>, which is a synchronous operation. |
2008 | |
2776 | |
2009 | For local paths, this usually doesn't matter: unless the system is very |
2777 | For local paths, this usually doesn't matter: unless the system is very |
2010 | busy or the intervals between stat's are large, a stat call will be fast, |
2778 | busy or the intervals between stat's are large, a stat call will be fast, |
2011 | as the path data is suually in memory already (except when starting the |
2779 | as the path data is usually in memory already (except when starting the |
2012 | watcher). |
2780 | watcher). |
2013 | |
2781 | |
2014 | For networked file systems, calling C<stat ()> can block an indefinite |
2782 | For networked file systems, calling C<stat ()> can block an indefinite |
2015 | time due to network issues, and even under good conditions, a stat call |
2783 | time due to network issues, and even under good conditions, a stat call |
2016 | often takes multiple milliseconds. |
2784 | often takes multiple milliseconds. |
… | |
… | |
2169 | Apart from keeping your process non-blocking (which is a useful |
2937 | Apart from keeping your process non-blocking (which is a useful |
2170 | effect on its own sometimes), idle watchers are a good place to do |
2938 | effect on its own sometimes), idle watchers are a good place to do |
2171 | "pseudo-background processing", or delay processing stuff to after the |
2939 | "pseudo-background processing", or delay processing stuff to after the |
2172 | event loop has handled all outstanding events. |
2940 | event loop has handled all outstanding events. |
2173 | |
2941 | |
|
|
2942 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2943 | |
|
|
2944 | As long as there is at least one active idle watcher, libev will never |
|
|
2945 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2946 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2947 | lowest priority will do. |
|
|
2948 | |
|
|
2949 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2950 | to do something on each event loop iteration - for example to balance load |
|
|
2951 | between different connections. |
|
|
2952 | |
|
|
2953 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2954 | example. |
|
|
2955 | |
2174 | =head3 Watcher-Specific Functions and Data Members |
2956 | =head3 Watcher-Specific Functions and Data Members |
2175 | |
2957 | |
2176 | =over 4 |
2958 | =over 4 |
2177 | |
2959 | |
2178 | =item ev_idle_init (ev_signal *, callback) |
2960 | =item ev_idle_init (ev_idle *, callback) |
2179 | |
2961 | |
2180 | Initialises and configures the idle watcher - it has no parameters of any |
2962 | Initialises and configures the idle watcher - it has no parameters of any |
2181 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2963 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2182 | believe me. |
2964 | believe me. |
2183 | |
2965 | |
… | |
… | |
2189 | callback, free it. Also, use no error checking, as usual. |
2971 | callback, free it. Also, use no error checking, as usual. |
2190 | |
2972 | |
2191 | static void |
2973 | static void |
2192 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2974 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2193 | { |
2975 | { |
|
|
2976 | // stop the watcher |
|
|
2977 | ev_idle_stop (loop, w); |
|
|
2978 | |
|
|
2979 | // now we can free it |
2194 | free (w); |
2980 | free (w); |
|
|
2981 | |
2195 | // now do something you wanted to do when the program has |
2982 | // now do something you wanted to do when the program has |
2196 | // no longer anything immediate to do. |
2983 | // no longer anything immediate to do. |
2197 | } |
2984 | } |
2198 | |
2985 | |
2199 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2986 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2200 | ev_idle_init (idle_watcher, idle_cb); |
2987 | ev_idle_init (idle_watcher, idle_cb); |
2201 | ev_idle_start (loop, idle_cb); |
2988 | ev_idle_start (loop, idle_watcher); |
2202 | |
2989 | |
2203 | |
2990 | |
2204 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2991 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2205 | |
2992 | |
2206 | Prepare and check watchers are usually (but not always) used in pairs: |
2993 | Prepare and check watchers are often (but not always) used in pairs: |
2207 | prepare watchers get invoked before the process blocks and check watchers |
2994 | prepare watchers get invoked before the process blocks and check watchers |
2208 | afterwards. |
2995 | afterwards. |
2209 | |
2996 | |
2210 | You I<must not> call C<ev_loop> or similar functions that enter |
2997 | You I<must not> call C<ev_run> (or similar functions that enter the |
2211 | the current event loop from either C<ev_prepare> or C<ev_check> |
2998 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2212 | watchers. Other loops than the current one are fine, however. The |
2999 | C<ev_check> watchers. Other loops than the current one are fine, |
2213 | rationale behind this is that you do not need to check for recursion in |
3000 | however. The rationale behind this is that you do not need to check |
2214 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3001 | for recursion in those watchers, i.e. the sequence will always be |
2215 | C<ev_check> so if you have one watcher of each kind they will always be |
3002 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2216 | called in pairs bracketing the blocking call. |
3003 | kind they will always be called in pairs bracketing the blocking call. |
2217 | |
3004 | |
2218 | Their main purpose is to integrate other event mechanisms into libev and |
3005 | Their main purpose is to integrate other event mechanisms into libev and |
2219 | their use is somewhat advanced. They could be used, for example, to track |
3006 | their use is somewhat advanced. They could be used, for example, to track |
2220 | variable changes, implement your own watchers, integrate net-snmp or a |
3007 | variable changes, implement your own watchers, integrate net-snmp or a |
2221 | coroutine library and lots more. They are also occasionally useful if |
3008 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2239 | with priority higher than or equal to the event loop and one coroutine |
3026 | with priority higher than or equal to the event loop and one coroutine |
2240 | of lower priority, but only once, using idle watchers to keep the event |
3027 | of lower priority, but only once, using idle watchers to keep the event |
2241 | loop from blocking if lower-priority coroutines are active, thus mapping |
3028 | loop from blocking if lower-priority coroutines are active, thus mapping |
2242 | low-priority coroutines to idle/background tasks). |
3029 | low-priority coroutines to idle/background tasks). |
2243 | |
3030 | |
2244 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3031 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2245 | priority, to ensure that they are being run before any other watchers |
3032 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2246 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3033 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3034 | watchers). |
2247 | |
3035 | |
2248 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3036 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2249 | activate ("feed") events into libev. While libev fully supports this, they |
3037 | activate ("feed") events into libev. While libev fully supports this, they |
2250 | might get executed before other C<ev_check> watchers did their job. As |
3038 | might get executed before other C<ev_check> watchers did their job. As |
2251 | C<ev_check> watchers are often used to embed other (non-libev) event |
3039 | C<ev_check> watchers are often used to embed other (non-libev) event |
2252 | loops those other event loops might be in an unusable state until their |
3040 | loops those other event loops might be in an unusable state until their |
2253 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3041 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2254 | others). |
3042 | others). |
|
|
3043 | |
|
|
3044 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3045 | |
|
|
3046 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3047 | useful because they are called once per event loop iteration. For |
|
|
3048 | example, if you want to handle a large number of connections fairly, you |
|
|
3049 | normally only do a bit of work for each active connection, and if there |
|
|
3050 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3051 | connections have a chance of making progress. |
|
|
3052 | |
|
|
3053 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3054 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3055 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3056 | |
|
|
3057 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3058 | single global idle watcher that is active as long as you have one active |
|
|
3059 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3060 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3061 | invoked. Neither watcher alone can do that. |
2255 | |
3062 | |
2256 | =head3 Watcher-Specific Functions and Data Members |
3063 | =head3 Watcher-Specific Functions and Data Members |
2257 | |
3064 | |
2258 | =over 4 |
3065 | =over 4 |
2259 | |
3066 | |
… | |
… | |
2299 | struct pollfd fds [nfd]; |
3106 | struct pollfd fds [nfd]; |
2300 | // actual code will need to loop here and realloc etc. |
3107 | // actual code will need to loop here and realloc etc. |
2301 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
3108 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2302 | |
3109 | |
2303 | /* the callback is illegal, but won't be called as we stop during check */ |
3110 | /* the callback is illegal, but won't be called as we stop during check */ |
2304 | ev_timer_init (&tw, 0, timeout * 1e-3); |
3111 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2305 | ev_timer_start (loop, &tw); |
3112 | ev_timer_start (loop, &tw); |
2306 | |
3113 | |
2307 | // create one ev_io per pollfd |
3114 | // create one ev_io per pollfd |
2308 | for (int i = 0; i < nfd; ++i) |
3115 | for (int i = 0; i < nfd; ++i) |
2309 | { |
3116 | { |
… | |
… | |
2383 | |
3190 | |
2384 | if (timeout >= 0) |
3191 | if (timeout >= 0) |
2385 | // create/start timer |
3192 | // create/start timer |
2386 | |
3193 | |
2387 | // poll |
3194 | // poll |
2388 | ev_loop (EV_A_ 0); |
3195 | ev_run (EV_A_ 0); |
2389 | |
3196 | |
2390 | // stop timer again |
3197 | // stop timer again |
2391 | if (timeout >= 0) |
3198 | if (timeout >= 0) |
2392 | ev_timer_stop (EV_A_ &to); |
3199 | ev_timer_stop (EV_A_ &to); |
2393 | |
3200 | |
… | |
… | |
2422 | some fds have to be watched and handled very quickly (with low latency), |
3229 | some fds have to be watched and handled very quickly (with low latency), |
2423 | and even priorities and idle watchers might have too much overhead. In |
3230 | and even priorities and idle watchers might have too much overhead. In |
2424 | this case you would put all the high priority stuff in one loop and all |
3231 | this case you would put all the high priority stuff in one loop and all |
2425 | the rest in a second one, and embed the second one in the first. |
3232 | the rest in a second one, and embed the second one in the first. |
2426 | |
3233 | |
2427 | As long as the watcher is active, the callback will be invoked every time |
3234 | As long as the watcher is active, the callback will be invoked every |
2428 | there might be events pending in the embedded loop. The callback must then |
3235 | time there might be events pending in the embedded loop. The callback |
2429 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
3236 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2430 | their callbacks (you could also start an idle watcher to give the embedded |
3237 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2431 | loop strictly lower priority for example). You can also set the callback |
3238 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2432 | to C<0>, in which case the embed watcher will automatically execute the |
3239 | to give the embedded loop strictly lower priority for example). |
2433 | embedded loop sweep. |
|
|
2434 | |
3240 | |
2435 | As long as the watcher is started it will automatically handle events. The |
3241 | You can also set the callback to C<0>, in which case the embed watcher |
2436 | callback will be invoked whenever some events have been handled. You can |
3242 | will automatically execute the embedded loop sweep whenever necessary. |
2437 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2438 | interested in that. |
|
|
2439 | |
3243 | |
2440 | Also, there have not currently been made special provisions for forking: |
3244 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2441 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
3245 | is active, i.e., the embedded loop will automatically be forked when the |
2442 | but you will also have to stop and restart any C<ev_embed> watchers |
3246 | embedding loop forks. In other cases, the user is responsible for calling |
2443 | yourself - but you can use a fork watcher to handle this automatically, |
3247 | C<ev_loop_fork> on the embedded loop. |
2444 | and future versions of libev might do just that. |
|
|
2445 | |
3248 | |
2446 | Unfortunately, not all backends are embeddable: only the ones returned by |
3249 | Unfortunately, not all backends are embeddable: only the ones returned by |
2447 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
3250 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2448 | portable one. |
3251 | portable one. |
2449 | |
3252 | |
… | |
… | |
2464 | |
3267 | |
2465 | =over 4 |
3268 | =over 4 |
2466 | |
3269 | |
2467 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3270 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2468 | |
3271 | |
2469 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3272 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2470 | |
3273 | |
2471 | Configures the watcher to embed the given loop, which must be |
3274 | Configures the watcher to embed the given loop, which must be |
2472 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3275 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2473 | invoked automatically, otherwise it is the responsibility of the callback |
3276 | invoked automatically, otherwise it is the responsibility of the callback |
2474 | to invoke it (it will continue to be called until the sweep has been done, |
3277 | to invoke it (it will continue to be called until the sweep has been done, |
2475 | if you do not want that, you need to temporarily stop the embed watcher). |
3278 | if you do not want that, you need to temporarily stop the embed watcher). |
2476 | |
3279 | |
2477 | =item ev_embed_sweep (loop, ev_embed *) |
3280 | =item ev_embed_sweep (loop, ev_embed *) |
2478 | |
3281 | |
2479 | Make a single, non-blocking sweep over the embedded loop. This works |
3282 | Make a single, non-blocking sweep over the embedded loop. This works |
2480 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3283 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2481 | appropriate way for embedded loops. |
3284 | appropriate way for embedded loops. |
2482 | |
3285 | |
2483 | =item struct ev_loop *other [read-only] |
3286 | =item struct ev_loop *other [read-only] |
2484 | |
3287 | |
2485 | The embedded event loop. |
3288 | The embedded event loop. |
… | |
… | |
2495 | used). |
3298 | used). |
2496 | |
3299 | |
2497 | struct ev_loop *loop_hi = ev_default_init (0); |
3300 | struct ev_loop *loop_hi = ev_default_init (0); |
2498 | struct ev_loop *loop_lo = 0; |
3301 | struct ev_loop *loop_lo = 0; |
2499 | ev_embed embed; |
3302 | ev_embed embed; |
2500 | |
3303 | |
2501 | // see if there is a chance of getting one that works |
3304 | // see if there is a chance of getting one that works |
2502 | // (remember that a flags value of 0 means autodetection) |
3305 | // (remember that a flags value of 0 means autodetection) |
2503 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3306 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2504 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3307 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2505 | : 0; |
3308 | : 0; |
… | |
… | |
2519 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3322 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2520 | |
3323 | |
2521 | struct ev_loop *loop = ev_default_init (0); |
3324 | struct ev_loop *loop = ev_default_init (0); |
2522 | struct ev_loop *loop_socket = 0; |
3325 | struct ev_loop *loop_socket = 0; |
2523 | ev_embed embed; |
3326 | ev_embed embed; |
2524 | |
3327 | |
2525 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3328 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2526 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3329 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2527 | { |
3330 | { |
2528 | ev_embed_init (&embed, 0, loop_socket); |
3331 | ev_embed_init (&embed, 0, loop_socket); |
2529 | ev_embed_start (loop, &embed); |
3332 | ev_embed_start (loop, &embed); |
… | |
… | |
2537 | |
3340 | |
2538 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3341 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2539 | |
3342 | |
2540 | Fork watchers are called when a C<fork ()> was detected (usually because |
3343 | Fork watchers are called when a C<fork ()> was detected (usually because |
2541 | whoever is a good citizen cared to tell libev about it by calling |
3344 | whoever is a good citizen cared to tell libev about it by calling |
2542 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3345 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
2543 | event loop blocks next and before C<ev_check> watchers are being called, |
3346 | and before C<ev_check> watchers are being called, and only in the child |
2544 | and only in the child after the fork. If whoever good citizen calling |
3347 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
2545 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3348 | and calls it in the wrong process, the fork handlers will be invoked, too, |
2546 | handlers will be invoked, too, of course. |
3349 | of course. |
|
|
3350 | |
|
|
3351 | =head3 The special problem of life after fork - how is it possible? |
|
|
3352 | |
|
|
3353 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
|
|
3354 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3355 | sequence should be handled by libev without any problems. |
|
|
3356 | |
|
|
3357 | This changes when the application actually wants to do event handling |
|
|
3358 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3359 | fork. |
|
|
3360 | |
|
|
3361 | The default mode of operation (for libev, with application help to detect |
|
|
3362 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3363 | when I<either> the parent I<or> the child process continues. |
|
|
3364 | |
|
|
3365 | When both processes want to continue using libev, then this is usually the |
|
|
3366 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3367 | supposed to continue with all watchers in place as before, while the other |
|
|
3368 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3369 | |
|
|
3370 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3371 | simply create a new event loop, which of course will be "empty", and |
|
|
3372 | use that for new watchers. This has the advantage of not touching more |
|
|
3373 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3374 | disadvantage of having to use multiple event loops (which do not support |
|
|
3375 | signal watchers). |
|
|
3376 | |
|
|
3377 | When this is not possible, or you want to use the default loop for |
|
|
3378 | other reasons, then in the process that wants to start "fresh", call |
|
|
3379 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3380 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3381 | watchers, so you have to be careful not to execute code that modifies |
|
|
3382 | those watchers. Note also that in that case, you have to re-register any |
|
|
3383 | signal watchers. |
2547 | |
3384 | |
2548 | =head3 Watcher-Specific Functions and Data Members |
3385 | =head3 Watcher-Specific Functions and Data Members |
2549 | |
3386 | |
2550 | =over 4 |
3387 | =over 4 |
2551 | |
3388 | |
2552 | =item ev_fork_init (ev_signal *, callback) |
3389 | =item ev_fork_init (ev_fork *, callback) |
2553 | |
3390 | |
2554 | Initialises and configures the fork watcher - it has no parameters of any |
3391 | Initialises and configures the fork watcher - it has no parameters of any |
2555 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3392 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2556 | believe me. |
3393 | really. |
2557 | |
3394 | |
2558 | =back |
3395 | =back |
2559 | |
3396 | |
2560 | |
3397 | |
|
|
3398 | =head2 C<ev_cleanup> - even the best things end |
|
|
3399 | |
|
|
3400 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3401 | by a call to C<ev_loop_destroy>. |
|
|
3402 | |
|
|
3403 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3404 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3405 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3406 | loop when you want them to be invoked. |
|
|
3407 | |
|
|
3408 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3409 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3410 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3411 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3412 | |
|
|
3413 | =head3 Watcher-Specific Functions and Data Members |
|
|
3414 | |
|
|
3415 | =over 4 |
|
|
3416 | |
|
|
3417 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3418 | |
|
|
3419 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3420 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3421 | pointless, I assure you. |
|
|
3422 | |
|
|
3423 | =back |
|
|
3424 | |
|
|
3425 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3426 | cleanup functions are called. |
|
|
3427 | |
|
|
3428 | static void |
|
|
3429 | program_exits (void) |
|
|
3430 | { |
|
|
3431 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3432 | } |
|
|
3433 | |
|
|
3434 | ... |
|
|
3435 | atexit (program_exits); |
|
|
3436 | |
|
|
3437 | |
2561 | =head2 C<ev_async> - how to wake up another event loop |
3438 | =head2 C<ev_async> - how to wake up an event loop |
2562 | |
3439 | |
2563 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3440 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2564 | asynchronous sources such as signal handlers (as opposed to multiple event |
3441 | asynchronous sources such as signal handlers (as opposed to multiple event |
2565 | loops - those are of course safe to use in different threads). |
3442 | loops - those are of course safe to use in different threads). |
2566 | |
3443 | |
2567 | Sometimes, however, you need to wake up another event loop you do not |
3444 | Sometimes, however, you need to wake up an event loop you do not control, |
2568 | control, for example because it belongs to another thread. This is what |
3445 | for example because it belongs to another thread. This is what C<ev_async> |
2569 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3446 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2570 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3447 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2571 | safe. |
|
|
2572 | |
3448 | |
2573 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3449 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2574 | too, are asynchronous in nature, and signals, too, will be compressed |
3450 | too, are asynchronous in nature, and signals, too, will be compressed |
2575 | (i.e. the number of callback invocations may be less than the number of |
3451 | (i.e. the number of callback invocations may be less than the number of |
2576 | C<ev_async_sent> calls). |
3452 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
2577 | |
3453 | of "global async watchers" by using a watcher on an otherwise unused |
2578 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3454 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2579 | just the default loop. |
3455 | even without knowing which loop owns the signal. |
2580 | |
3456 | |
2581 | =head3 Queueing |
3457 | =head3 Queueing |
2582 | |
3458 | |
2583 | C<ev_async> does not support queueing of data in any way. The reason |
3459 | C<ev_async> does not support queueing of data in any way. The reason |
2584 | is that the author does not know of a simple (or any) algorithm for a |
3460 | is that the author does not know of a simple (or any) algorithm for a |
2585 | multiple-writer-single-reader queue that works in all cases and doesn't |
3461 | multiple-writer-single-reader queue that works in all cases and doesn't |
2586 | need elaborate support such as pthreads. |
3462 | need elaborate support such as pthreads or unportable memory access |
|
|
3463 | semantics. |
2587 | |
3464 | |
2588 | That means that if you want to queue data, you have to provide your own |
3465 | That means that if you want to queue data, you have to provide your own |
2589 | queue. But at least I can tell you how to implement locking around your |
3466 | queue. But at least I can tell you how to implement locking around your |
2590 | queue: |
3467 | queue: |
2591 | |
3468 | |
… | |
… | |
2675 | trust me. |
3552 | trust me. |
2676 | |
3553 | |
2677 | =item ev_async_send (loop, ev_async *) |
3554 | =item ev_async_send (loop, ev_async *) |
2678 | |
3555 | |
2679 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3556 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2680 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3557 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3558 | returns. |
|
|
3559 | |
2681 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3560 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2682 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3561 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2683 | section below on what exactly this means). |
3562 | embedding section below on what exactly this means). |
2684 | |
3563 | |
2685 | This call incurs the overhead of a system call only once per loop iteration, |
3564 | Note that, as with other watchers in libev, multiple events might get |
2686 | so while the overhead might be noticeable, it doesn't apply to repeated |
3565 | compressed into a single callback invocation (another way to look at |
2687 | calls to C<ev_async_send>. |
3566 | this is that C<ev_async> watchers are level-triggered: they are set on |
|
|
3567 | C<ev_async_send>, reset when the event loop detects that). |
|
|
3568 | |
|
|
3569 | This call incurs the overhead of at most one extra system call per event |
|
|
3570 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3571 | the event loop (or your program) is processing events. That means that |
|
|
3572 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3573 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3574 | zero) under load. |
2688 | |
3575 | |
2689 | =item bool = ev_async_pending (ev_async *) |
3576 | =item bool = ev_async_pending (ev_async *) |
2690 | |
3577 | |
2691 | Returns a non-zero value when C<ev_async_send> has been called on the |
3578 | Returns a non-zero value when C<ev_async_send> has been called on the |
2692 | watcher but the event has not yet been processed (or even noted) by the |
3579 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2695 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3582 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2696 | the loop iterates next and checks for the watcher to have become active, |
3583 | the loop iterates next and checks for the watcher to have become active, |
2697 | it will reset the flag again. C<ev_async_pending> can be used to very |
3584 | it will reset the flag again. C<ev_async_pending> can be used to very |
2698 | quickly check whether invoking the loop might be a good idea. |
3585 | quickly check whether invoking the loop might be a good idea. |
2699 | |
3586 | |
2700 | Not that this does I<not> check whether the watcher itself is pending, only |
3587 | Not that this does I<not> check whether the watcher itself is pending, |
2701 | whether it has been requested to make this watcher pending. |
3588 | only whether it has been requested to make this watcher pending: there |
|
|
3589 | is a time window between the event loop checking and resetting the async |
|
|
3590 | notification, and the callback being invoked. |
2702 | |
3591 | |
2703 | =back |
3592 | =back |
2704 | |
3593 | |
2705 | |
3594 | |
2706 | =head1 OTHER FUNCTIONS |
3595 | =head1 OTHER FUNCTIONS |
2707 | |
3596 | |
2708 | There are some other functions of possible interest. Described. Here. Now. |
3597 | There are some other functions of possible interest. Described. Here. Now. |
2709 | |
3598 | |
2710 | =over 4 |
3599 | =over 4 |
2711 | |
3600 | |
2712 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3601 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
2713 | |
3602 | |
2714 | This function combines a simple timer and an I/O watcher, calls your |
3603 | This function combines a simple timer and an I/O watcher, calls your |
2715 | callback on whichever event happens first and automatically stops both |
3604 | callback on whichever event happens first and automatically stops both |
2716 | watchers. This is useful if you want to wait for a single event on an fd |
3605 | watchers. This is useful if you want to wait for a single event on an fd |
2717 | or timeout without having to allocate/configure/start/stop/free one or |
3606 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
2723 | |
3612 | |
2724 | If C<timeout> is less than 0, then no timeout watcher will be |
3613 | If C<timeout> is less than 0, then no timeout watcher will be |
2725 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3614 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2726 | repeat = 0) will be started. C<0> is a valid timeout. |
3615 | repeat = 0) will be started. C<0> is a valid timeout. |
2727 | |
3616 | |
2728 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3617 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2729 | passed an C<revents> set like normal event callbacks (a combination of |
3618 | passed an C<revents> set like normal event callbacks (a combination of |
2730 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3619 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2731 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3620 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2732 | a timeout and an io event at the same time - you probably should give io |
3621 | a timeout and an io event at the same time - you probably should give io |
2733 | events precedence. |
3622 | events precedence. |
2734 | |
3623 | |
2735 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3624 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2736 | |
3625 | |
2737 | static void stdin_ready (int revents, void *arg) |
3626 | static void stdin_ready (int revents, void *arg) |
2738 | { |
3627 | { |
2739 | if (revents & EV_READ) |
3628 | if (revents & EV_READ) |
2740 | /* stdin might have data for us, joy! */; |
3629 | /* stdin might have data for us, joy! */; |
2741 | else if (revents & EV_TIMEOUT) |
3630 | else if (revents & EV_TIMER) |
2742 | /* doh, nothing entered */; |
3631 | /* doh, nothing entered */; |
2743 | } |
3632 | } |
2744 | |
3633 | |
2745 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3634 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2746 | |
3635 | |
2747 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2748 | |
|
|
2749 | Feeds the given event set into the event loop, as if the specified event |
|
|
2750 | had happened for the specified watcher (which must be a pointer to an |
|
|
2751 | initialised but not necessarily started event watcher). |
|
|
2752 | |
|
|
2753 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3636 | =item ev_feed_fd_event (loop, int fd, int revents) |
2754 | |
3637 | |
2755 | Feed an event on the given fd, as if a file descriptor backend detected |
3638 | Feed an event on the given fd, as if a file descriptor backend detected |
2756 | the given events it. |
3639 | the given events. |
2757 | |
3640 | |
2758 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3641 | =item ev_feed_signal_event (loop, int signum) |
2759 | |
3642 | |
2760 | Feed an event as if the given signal occurred (C<loop> must be the default |
3643 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
2761 | loop!). |
3644 | which is async-safe. |
2762 | |
3645 | |
2763 | =back |
3646 | =back |
|
|
3647 | |
|
|
3648 | |
|
|
3649 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3650 | |
|
|
3651 | This section explains some common idioms that are not immediately |
|
|
3652 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3653 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3654 | |
|
|
3655 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3656 | |
|
|
3657 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3658 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3659 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3660 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3661 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3662 | data: |
|
|
3663 | |
|
|
3664 | struct my_io |
|
|
3665 | { |
|
|
3666 | ev_io io; |
|
|
3667 | int otherfd; |
|
|
3668 | void *somedata; |
|
|
3669 | struct whatever *mostinteresting; |
|
|
3670 | }; |
|
|
3671 | |
|
|
3672 | ... |
|
|
3673 | struct my_io w; |
|
|
3674 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3675 | |
|
|
3676 | And since your callback will be called with a pointer to the watcher, you |
|
|
3677 | can cast it back to your own type: |
|
|
3678 | |
|
|
3679 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3680 | { |
|
|
3681 | struct my_io *w = (struct my_io *)w_; |
|
|
3682 | ... |
|
|
3683 | } |
|
|
3684 | |
|
|
3685 | More interesting and less C-conformant ways of casting your callback |
|
|
3686 | function type instead have been omitted. |
|
|
3687 | |
|
|
3688 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3689 | |
|
|
3690 | Another common scenario is to use some data structure with multiple |
|
|
3691 | embedded watchers, in effect creating your own watcher that combines |
|
|
3692 | multiple libev event sources into one "super-watcher": |
|
|
3693 | |
|
|
3694 | struct my_biggy |
|
|
3695 | { |
|
|
3696 | int some_data; |
|
|
3697 | ev_timer t1; |
|
|
3698 | ev_timer t2; |
|
|
3699 | } |
|
|
3700 | |
|
|
3701 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3702 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3703 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3704 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3705 | real programmers): |
|
|
3706 | |
|
|
3707 | #include <stddef.h> |
|
|
3708 | |
|
|
3709 | static void |
|
|
3710 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3711 | { |
|
|
3712 | struct my_biggy big = (struct my_biggy *) |
|
|
3713 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3714 | } |
|
|
3715 | |
|
|
3716 | static void |
|
|
3717 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3718 | { |
|
|
3719 | struct my_biggy big = (struct my_biggy *) |
|
|
3720 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3721 | } |
|
|
3722 | |
|
|
3723 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3724 | |
|
|
3725 | Often you have structures like this in event-based programs: |
|
|
3726 | |
|
|
3727 | callback () |
|
|
3728 | { |
|
|
3729 | free (request); |
|
|
3730 | } |
|
|
3731 | |
|
|
3732 | request = start_new_request (..., callback); |
|
|
3733 | |
|
|
3734 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3735 | used to cancel the operation, or do other things with it. |
|
|
3736 | |
|
|
3737 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3738 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3739 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3740 | operation and simply invoke the callback with the result. |
|
|
3741 | |
|
|
3742 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3743 | has returned, so C<request> is not set. |
|
|
3744 | |
|
|
3745 | Even if you pass the request by some safer means to the callback, you |
|
|
3746 | might want to do something to the request after starting it, such as |
|
|
3747 | canceling it, which probably isn't working so well when the callback has |
|
|
3748 | already been invoked. |
|
|
3749 | |
|
|
3750 | A common way around all these issues is to make sure that |
|
|
3751 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3752 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3753 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3754 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3755 | pushing it into the pending queue: |
|
|
3756 | |
|
|
3757 | ev_set_cb (watcher, callback); |
|
|
3758 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3759 | |
|
|
3760 | This way, C<start_new_request> can safely return before the callback is |
|
|
3761 | invoked, while not delaying callback invocation too much. |
|
|
3762 | |
|
|
3763 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3764 | |
|
|
3765 | Often (especially in GUI toolkits) there are places where you have |
|
|
3766 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3767 | invoking C<ev_run>. |
|
|
3768 | |
|
|
3769 | This brings the problem of exiting - a callback might want to finish the |
|
|
3770 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3771 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3772 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3773 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3774 | |
|
|
3775 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3776 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3777 | triggered, using C<EVRUN_ONCE>: |
|
|
3778 | |
|
|
3779 | // main loop |
|
|
3780 | int exit_main_loop = 0; |
|
|
3781 | |
|
|
3782 | while (!exit_main_loop) |
|
|
3783 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3784 | |
|
|
3785 | // in a modal watcher |
|
|
3786 | int exit_nested_loop = 0; |
|
|
3787 | |
|
|
3788 | while (!exit_nested_loop) |
|
|
3789 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3790 | |
|
|
3791 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3792 | |
|
|
3793 | // exit modal loop |
|
|
3794 | exit_nested_loop = 1; |
|
|
3795 | |
|
|
3796 | // exit main program, after modal loop is finished |
|
|
3797 | exit_main_loop = 1; |
|
|
3798 | |
|
|
3799 | // exit both |
|
|
3800 | exit_main_loop = exit_nested_loop = 1; |
|
|
3801 | |
|
|
3802 | =head2 THREAD LOCKING EXAMPLE |
|
|
3803 | |
|
|
3804 | Here is a fictitious example of how to run an event loop in a different |
|
|
3805 | thread from where callbacks are being invoked and watchers are |
|
|
3806 | created/added/removed. |
|
|
3807 | |
|
|
3808 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3809 | which uses exactly this technique (which is suited for many high-level |
|
|
3810 | languages). |
|
|
3811 | |
|
|
3812 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3813 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3814 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3815 | |
|
|
3816 | First, you need to associate some data with the event loop: |
|
|
3817 | |
|
|
3818 | typedef struct { |
|
|
3819 | mutex_t lock; /* global loop lock */ |
|
|
3820 | ev_async async_w; |
|
|
3821 | thread_t tid; |
|
|
3822 | cond_t invoke_cv; |
|
|
3823 | } userdata; |
|
|
3824 | |
|
|
3825 | void prepare_loop (EV_P) |
|
|
3826 | { |
|
|
3827 | // for simplicity, we use a static userdata struct. |
|
|
3828 | static userdata u; |
|
|
3829 | |
|
|
3830 | ev_async_init (&u->async_w, async_cb); |
|
|
3831 | ev_async_start (EV_A_ &u->async_w); |
|
|
3832 | |
|
|
3833 | pthread_mutex_init (&u->lock, 0); |
|
|
3834 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3835 | |
|
|
3836 | // now associate this with the loop |
|
|
3837 | ev_set_userdata (EV_A_ u); |
|
|
3838 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3839 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3840 | |
|
|
3841 | // then create the thread running ev_run |
|
|
3842 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3843 | } |
|
|
3844 | |
|
|
3845 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3846 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3847 | that might have been added: |
|
|
3848 | |
|
|
3849 | static void |
|
|
3850 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3851 | { |
|
|
3852 | // just used for the side effects |
|
|
3853 | } |
|
|
3854 | |
|
|
3855 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3856 | protecting the loop data, respectively. |
|
|
3857 | |
|
|
3858 | static void |
|
|
3859 | l_release (EV_P) |
|
|
3860 | { |
|
|
3861 | userdata *u = ev_userdata (EV_A); |
|
|
3862 | pthread_mutex_unlock (&u->lock); |
|
|
3863 | } |
|
|
3864 | |
|
|
3865 | static void |
|
|
3866 | l_acquire (EV_P) |
|
|
3867 | { |
|
|
3868 | userdata *u = ev_userdata (EV_A); |
|
|
3869 | pthread_mutex_lock (&u->lock); |
|
|
3870 | } |
|
|
3871 | |
|
|
3872 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3873 | into C<ev_run>: |
|
|
3874 | |
|
|
3875 | void * |
|
|
3876 | l_run (void *thr_arg) |
|
|
3877 | { |
|
|
3878 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3879 | |
|
|
3880 | l_acquire (EV_A); |
|
|
3881 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3882 | ev_run (EV_A_ 0); |
|
|
3883 | l_release (EV_A); |
|
|
3884 | |
|
|
3885 | return 0; |
|
|
3886 | } |
|
|
3887 | |
|
|
3888 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3889 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3890 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3891 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3892 | and b) skipping inter-thread-communication when there are no pending |
|
|
3893 | watchers is very beneficial): |
|
|
3894 | |
|
|
3895 | static void |
|
|
3896 | l_invoke (EV_P) |
|
|
3897 | { |
|
|
3898 | userdata *u = ev_userdata (EV_A); |
|
|
3899 | |
|
|
3900 | while (ev_pending_count (EV_A)) |
|
|
3901 | { |
|
|
3902 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3903 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3904 | } |
|
|
3905 | } |
|
|
3906 | |
|
|
3907 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3908 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3909 | thread to continue: |
|
|
3910 | |
|
|
3911 | static void |
|
|
3912 | real_invoke_pending (EV_P) |
|
|
3913 | { |
|
|
3914 | userdata *u = ev_userdata (EV_A); |
|
|
3915 | |
|
|
3916 | pthread_mutex_lock (&u->lock); |
|
|
3917 | ev_invoke_pending (EV_A); |
|
|
3918 | pthread_cond_signal (&u->invoke_cv); |
|
|
3919 | pthread_mutex_unlock (&u->lock); |
|
|
3920 | } |
|
|
3921 | |
|
|
3922 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3923 | event loop, you will now have to lock: |
|
|
3924 | |
|
|
3925 | ev_timer timeout_watcher; |
|
|
3926 | userdata *u = ev_userdata (EV_A); |
|
|
3927 | |
|
|
3928 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3929 | |
|
|
3930 | pthread_mutex_lock (&u->lock); |
|
|
3931 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3932 | ev_async_send (EV_A_ &u->async_w); |
|
|
3933 | pthread_mutex_unlock (&u->lock); |
|
|
3934 | |
|
|
3935 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3936 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3937 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3938 | watchers in the next event loop iteration. |
|
|
3939 | |
|
|
3940 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3941 | |
|
|
3942 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3943 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3944 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3945 | doesn't need callbacks anymore. |
|
|
3946 | |
|
|
3947 | Imagine you have coroutines that you can switch to using a function |
|
|
3948 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3949 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3950 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3951 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3952 | the differing C<;> conventions): |
|
|
3953 | |
|
|
3954 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3955 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3956 | |
|
|
3957 | That means instead of having a C callback function, you store the |
|
|
3958 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3959 | your callback, you instead have it switch to that coroutine. |
|
|
3960 | |
|
|
3961 | A coroutine might now wait for an event with a function called |
|
|
3962 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3963 | matter when, or whether the watcher is active or not when this function is |
|
|
3964 | called): |
|
|
3965 | |
|
|
3966 | void |
|
|
3967 | wait_for_event (ev_watcher *w) |
|
|
3968 | { |
|
|
3969 | ev_set_cb (w, current_coro); |
|
|
3970 | switch_to (libev_coro); |
|
|
3971 | } |
|
|
3972 | |
|
|
3973 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3974 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3975 | this or any other coroutine. |
|
|
3976 | |
|
|
3977 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3978 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3979 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3980 | any waiters. |
|
|
3981 | |
|
|
3982 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3983 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3984 | |
|
|
3985 | // my_ev.h |
|
|
3986 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3987 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3988 | #include "../libev/ev.h" |
|
|
3989 | |
|
|
3990 | // my_ev.c |
|
|
3991 | #define EV_H "my_ev.h" |
|
|
3992 | #include "../libev/ev.c" |
|
|
3993 | |
|
|
3994 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3995 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3996 | can even use F<ev.h> as header file name directly. |
2764 | |
3997 | |
2765 | |
3998 | |
2766 | =head1 LIBEVENT EMULATION |
3999 | =head1 LIBEVENT EMULATION |
2767 | |
4000 | |
2768 | Libev offers a compatibility emulation layer for libevent. It cannot |
4001 | Libev offers a compatibility emulation layer for libevent. It cannot |
2769 | emulate the internals of libevent, so here are some usage hints: |
4002 | emulate the internals of libevent, so here are some usage hints: |
2770 | |
4003 | |
2771 | =over 4 |
4004 | =over 4 |
|
|
4005 | |
|
|
4006 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
4007 | |
|
|
4008 | This was the newest libevent version available when libev was implemented, |
|
|
4009 | and is still mostly unchanged in 2010. |
2772 | |
4010 | |
2773 | =item * Use it by including <event.h>, as usual. |
4011 | =item * Use it by including <event.h>, as usual. |
2774 | |
4012 | |
2775 | =item * The following members are fully supported: ev_base, ev_callback, |
4013 | =item * The following members are fully supported: ev_base, ev_callback, |
2776 | ev_arg, ev_fd, ev_res, ev_events. |
4014 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2782 | =item * Priorities are not currently supported. Initialising priorities |
4020 | =item * Priorities are not currently supported. Initialising priorities |
2783 | will fail and all watchers will have the same priority, even though there |
4021 | will fail and all watchers will have the same priority, even though there |
2784 | is an ev_pri field. |
4022 | is an ev_pri field. |
2785 | |
4023 | |
2786 | =item * In libevent, the last base created gets the signals, in libev, the |
4024 | =item * In libevent, the last base created gets the signals, in libev, the |
2787 | first base created (== the default loop) gets the signals. |
4025 | base that registered the signal gets the signals. |
2788 | |
4026 | |
2789 | =item * Other members are not supported. |
4027 | =item * Other members are not supported. |
2790 | |
4028 | |
2791 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
4029 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2792 | to use the libev header file and library. |
4030 | to use the libev header file and library. |
2793 | |
4031 | |
2794 | =back |
4032 | =back |
2795 | |
4033 | |
2796 | =head1 C++ SUPPORT |
4034 | =head1 C++ SUPPORT |
|
|
4035 | |
|
|
4036 | =head2 C API |
|
|
4037 | |
|
|
4038 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4039 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4040 | will work fine. |
|
|
4041 | |
|
|
4042 | Proper exception specifications might have to be added to callbacks passed |
|
|
4043 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4044 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4045 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4046 | specification. If you have code that needs to be compiled as both C and |
|
|
4047 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4048 | |
|
|
4049 | static void |
|
|
4050 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4051 | { |
|
|
4052 | perror (msg); |
|
|
4053 | abort (); |
|
|
4054 | } |
|
|
4055 | |
|
|
4056 | ... |
|
|
4057 | ev_set_syserr_cb (fatal_error); |
|
|
4058 | |
|
|
4059 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4060 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4061 | because it runs cleanup watchers). |
|
|
4062 | |
|
|
4063 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4064 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4065 | throwing exceptions through C libraries (most do). |
|
|
4066 | |
|
|
4067 | =head2 C++ API |
2797 | |
4068 | |
2798 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4069 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2799 | you to use some convenience methods to start/stop watchers and also change |
4070 | you to use some convenience methods to start/stop watchers and also change |
2800 | the callback model to a model using method callbacks on objects. |
4071 | the callback model to a model using method callbacks on objects. |
2801 | |
4072 | |
2802 | To use it, |
4073 | To use it, |
2803 | |
4074 | |
2804 | #include <ev++.h> |
4075 | #include <ev++.h> |
2805 | |
4076 | |
2806 | This automatically includes F<ev.h> and puts all of its definitions (many |
4077 | This automatically includes F<ev.h> and puts all of its definitions (many |
2807 | of them macros) into the global namespace. All C++ specific things are |
4078 | of them macros) into the global namespace. All C++ specific things are |
2808 | put into the C<ev> namespace. It should support all the same embedding |
4079 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
2811 | Care has been taken to keep the overhead low. The only data member the C++ |
4082 | Care has been taken to keep the overhead low. The only data member the C++ |
2812 | classes add (compared to plain C-style watchers) is the event loop pointer |
4083 | classes add (compared to plain C-style watchers) is the event loop pointer |
2813 | that the watcher is associated with (or no additional members at all if |
4084 | that the watcher is associated with (or no additional members at all if |
2814 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4085 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2815 | |
4086 | |
2816 | Currently, functions, and static and non-static member functions can be |
4087 | Currently, functions, static and non-static member functions and classes |
2817 | used as callbacks. Other types should be easy to add as long as they only |
4088 | with C<operator ()> can be used as callbacks. Other types should be easy |
2818 | need one additional pointer for context. If you need support for other |
4089 | to add as long as they only need one additional pointer for context. If |
2819 | types of functors please contact the author (preferably after implementing |
4090 | you need support for other types of functors please contact the author |
2820 | it). |
4091 | (preferably after implementing it). |
|
|
4092 | |
|
|
4093 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4094 | conventions as your C compiler (for static member functions), or you have |
|
|
4095 | to embed libev and compile libev itself as C++. |
2821 | |
4096 | |
2822 | Here is a list of things available in the C<ev> namespace: |
4097 | Here is a list of things available in the C<ev> namespace: |
2823 | |
4098 | |
2824 | =over 4 |
4099 | =over 4 |
2825 | |
4100 | |
… | |
… | |
2835 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4110 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
2836 | |
4111 | |
2837 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4112 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
2838 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4113 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
2839 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4114 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
2840 | defines by many implementations. |
4115 | defined by many implementations. |
2841 | |
4116 | |
2842 | All of those classes have these methods: |
4117 | All of those classes have these methods: |
2843 | |
4118 | |
2844 | =over 4 |
4119 | =over 4 |
2845 | |
4120 | |
2846 | =item ev::TYPE::TYPE () |
4121 | =item ev::TYPE::TYPE () |
2847 | |
4122 | |
2848 | =item ev::TYPE::TYPE (struct ev_loop *) |
4123 | =item ev::TYPE::TYPE (loop) |
2849 | |
4124 | |
2850 | =item ev::TYPE::~TYPE |
4125 | =item ev::TYPE::~TYPE |
2851 | |
4126 | |
2852 | The constructor (optionally) takes an event loop to associate the watcher |
4127 | The constructor (optionally) takes an event loop to associate the watcher |
2853 | with. If it is omitted, it will use C<EV_DEFAULT>. |
4128 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2885 | |
4160 | |
2886 | myclass obj; |
4161 | myclass obj; |
2887 | ev::io iow; |
4162 | ev::io iow; |
2888 | iow.set <myclass, &myclass::io_cb> (&obj); |
4163 | iow.set <myclass, &myclass::io_cb> (&obj); |
2889 | |
4164 | |
|
|
4165 | =item w->set (object *) |
|
|
4166 | |
|
|
4167 | This is a variation of a method callback - leaving out the method to call |
|
|
4168 | will default the method to C<operator ()>, which makes it possible to use |
|
|
4169 | functor objects without having to manually specify the C<operator ()> all |
|
|
4170 | the time. Incidentally, you can then also leave out the template argument |
|
|
4171 | list. |
|
|
4172 | |
|
|
4173 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
4174 | int revents)>. |
|
|
4175 | |
|
|
4176 | See the method-C<set> above for more details. |
|
|
4177 | |
|
|
4178 | Example: use a functor object as callback. |
|
|
4179 | |
|
|
4180 | struct myfunctor |
|
|
4181 | { |
|
|
4182 | void operator() (ev::io &w, int revents) |
|
|
4183 | { |
|
|
4184 | ... |
|
|
4185 | } |
|
|
4186 | } |
|
|
4187 | |
|
|
4188 | myfunctor f; |
|
|
4189 | |
|
|
4190 | ev::io w; |
|
|
4191 | w.set (&f); |
|
|
4192 | |
2890 | =item w->set<function> (void *data = 0) |
4193 | =item w->set<function> (void *data = 0) |
2891 | |
4194 | |
2892 | Also sets a callback, but uses a static method or plain function as |
4195 | Also sets a callback, but uses a static method or plain function as |
2893 | callback. The optional C<data> argument will be stored in the watcher's |
4196 | callback. The optional C<data> argument will be stored in the watcher's |
2894 | C<data> member and is free for you to use. |
4197 | C<data> member and is free for you to use. |
… | |
… | |
2900 | Example: Use a plain function as callback. |
4203 | Example: Use a plain function as callback. |
2901 | |
4204 | |
2902 | static void io_cb (ev::io &w, int revents) { } |
4205 | static void io_cb (ev::io &w, int revents) { } |
2903 | iow.set <io_cb> (); |
4206 | iow.set <io_cb> (); |
2904 | |
4207 | |
2905 | =item w->set (struct ev_loop *) |
4208 | =item w->set (loop) |
2906 | |
4209 | |
2907 | Associates a different C<struct ev_loop> with this watcher. You can only |
4210 | Associates a different C<struct ev_loop> with this watcher. You can only |
2908 | do this when the watcher is inactive (and not pending either). |
4211 | do this when the watcher is inactive (and not pending either). |
2909 | |
4212 | |
2910 | =item w->set ([arguments]) |
4213 | =item w->set ([arguments]) |
2911 | |
4214 | |
2912 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
4215 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
|
|
4216 | with the same arguments. Either this method or a suitable start method |
2913 | called at least once. Unlike the C counterpart, an active watcher gets |
4217 | must be called at least once. Unlike the C counterpart, an active watcher |
2914 | automatically stopped and restarted when reconfiguring it with this |
4218 | gets automatically stopped and restarted when reconfiguring it with this |
2915 | method. |
4219 | method. |
|
|
4220 | |
|
|
4221 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4222 | clashing with the C<set (loop)> method. |
2916 | |
4223 | |
2917 | =item w->start () |
4224 | =item w->start () |
2918 | |
4225 | |
2919 | Starts the watcher. Note that there is no C<loop> argument, as the |
4226 | Starts the watcher. Note that there is no C<loop> argument, as the |
2920 | constructor already stores the event loop. |
4227 | constructor already stores the event loop. |
2921 | |
4228 | |
|
|
4229 | =item w->start ([arguments]) |
|
|
4230 | |
|
|
4231 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4232 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4233 | the configure C<set> method of the watcher. |
|
|
4234 | |
2922 | =item w->stop () |
4235 | =item w->stop () |
2923 | |
4236 | |
2924 | Stops the watcher if it is active. Again, no C<loop> argument. |
4237 | Stops the watcher if it is active. Again, no C<loop> argument. |
2925 | |
4238 | |
2926 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4239 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2938 | |
4251 | |
2939 | =back |
4252 | =back |
2940 | |
4253 | |
2941 | =back |
4254 | =back |
2942 | |
4255 | |
2943 | Example: Define a class with an IO and idle watcher, start one of them in |
4256 | Example: Define a class with two I/O and idle watchers, start the I/O |
2944 | the constructor. |
4257 | watchers in the constructor. |
2945 | |
4258 | |
2946 | class myclass |
4259 | class myclass |
2947 | { |
4260 | { |
2948 | ev::io io ; void io_cb (ev::io &w, int revents); |
4261 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4262 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
2949 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4263 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2950 | |
4264 | |
2951 | myclass (int fd) |
4265 | myclass (int fd) |
2952 | { |
4266 | { |
2953 | io .set <myclass, &myclass::io_cb > (this); |
4267 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4268 | io2 .set <myclass, &myclass::io2_cb > (this); |
2954 | idle.set <myclass, &myclass::idle_cb> (this); |
4269 | idle.set <myclass, &myclass::idle_cb> (this); |
2955 | |
4270 | |
2956 | io.start (fd, ev::READ); |
4271 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4272 | io.start (); // start it whenever convenient |
|
|
4273 | |
|
|
4274 | io2.start (fd, ev::READ); // set + start in one call |
2957 | } |
4275 | } |
2958 | }; |
4276 | }; |
2959 | |
4277 | |
2960 | |
4278 | |
2961 | =head1 OTHER LANGUAGE BINDINGS |
4279 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2980 | L<http://software.schmorp.de/pkg/EV>. |
4298 | L<http://software.schmorp.de/pkg/EV>. |
2981 | |
4299 | |
2982 | =item Python |
4300 | =item Python |
2983 | |
4301 | |
2984 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
4302 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2985 | seems to be quite complete and well-documented. Note, however, that the |
4303 | seems to be quite complete and well-documented. |
2986 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2987 | for everybody else, and therefore, should never be applied in an installed |
|
|
2988 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2989 | libev). |
|
|
2990 | |
4304 | |
2991 | =item Ruby |
4305 | =item Ruby |
2992 | |
4306 | |
2993 | Tony Arcieri has written a ruby extension that offers access to a subset |
4307 | Tony Arcieri has written a ruby extension that offers access to a subset |
2994 | of the libev API and adds file handle abstractions, asynchronous DNS and |
4308 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2995 | more on top of it. It can be found via gem servers. Its homepage is at |
4309 | more on top of it. It can be found via gem servers. Its homepage is at |
2996 | L<http://rev.rubyforge.org/>. |
4310 | L<http://rev.rubyforge.org/>. |
2997 | |
4311 | |
|
|
4312 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
4313 | makes rev work even on mingw. |
|
|
4314 | |
|
|
4315 | =item Haskell |
|
|
4316 | |
|
|
4317 | A haskell binding to libev is available at |
|
|
4318 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
4319 | |
2998 | =item D |
4320 | =item D |
2999 | |
4321 | |
3000 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4322 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3001 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4323 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3002 | |
4324 | |
3003 | =item Ocaml |
4325 | =item Ocaml |
3004 | |
4326 | |
3005 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4327 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3006 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4328 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4329 | |
|
|
4330 | =item Lua |
|
|
4331 | |
|
|
4332 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4333 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4334 | L<http://github.com/brimworks/lua-ev>. |
|
|
4335 | |
|
|
4336 | =item Javascript |
|
|
4337 | |
|
|
4338 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4339 | |
|
|
4340 | =item Others |
|
|
4341 | |
|
|
4342 | There are others, and I stopped counting. |
3007 | |
4343 | |
3008 | =back |
4344 | =back |
3009 | |
4345 | |
3010 | |
4346 | |
3011 | =head1 MACRO MAGIC |
4347 | =head1 MACRO MAGIC |
… | |
… | |
3025 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4361 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3026 | C<EV_A_> is used when other arguments are following. Example: |
4362 | C<EV_A_> is used when other arguments are following. Example: |
3027 | |
4363 | |
3028 | ev_unref (EV_A); |
4364 | ev_unref (EV_A); |
3029 | ev_timer_add (EV_A_ watcher); |
4365 | ev_timer_add (EV_A_ watcher); |
3030 | ev_loop (EV_A_ 0); |
4366 | ev_run (EV_A_ 0); |
3031 | |
4367 | |
3032 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4368 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3033 | which is often provided by the following macro. |
4369 | which is often provided by the following macro. |
3034 | |
4370 | |
3035 | =item C<EV_P>, C<EV_P_> |
4371 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3048 | suitable for use with C<EV_A>. |
4384 | suitable for use with C<EV_A>. |
3049 | |
4385 | |
3050 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4386 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3051 | |
4387 | |
3052 | Similar to the other two macros, this gives you the value of the default |
4388 | Similar to the other two macros, this gives you the value of the default |
3053 | loop, if multiple loops are supported ("ev loop default"). |
4389 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4390 | will be initialised if it isn't already initialised. |
|
|
4391 | |
|
|
4392 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4393 | to initialise the loop somewhere. |
3054 | |
4394 | |
3055 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4395 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3056 | |
4396 | |
3057 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4397 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3058 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4398 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3075 | } |
4415 | } |
3076 | |
4416 | |
3077 | ev_check check; |
4417 | ev_check check; |
3078 | ev_check_init (&check, check_cb); |
4418 | ev_check_init (&check, check_cb); |
3079 | ev_check_start (EV_DEFAULT_ &check); |
4419 | ev_check_start (EV_DEFAULT_ &check); |
3080 | ev_loop (EV_DEFAULT_ 0); |
4420 | ev_run (EV_DEFAULT_ 0); |
3081 | |
4421 | |
3082 | =head1 EMBEDDING |
4422 | =head1 EMBEDDING |
3083 | |
4423 | |
3084 | Libev can (and often is) directly embedded into host |
4424 | Libev can (and often is) directly embedded into host |
3085 | applications. Examples of applications that embed it include the Deliantra |
4425 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3125 | ev_vars.h |
4465 | ev_vars.h |
3126 | ev_wrap.h |
4466 | ev_wrap.h |
3127 | |
4467 | |
3128 | ev_win32.c required on win32 platforms only |
4468 | ev_win32.c required on win32 platforms only |
3129 | |
4469 | |
3130 | ev_select.c only when select backend is enabled (which is enabled by default) |
4470 | ev_select.c only when select backend is enabled |
3131 | ev_poll.c only when poll backend is enabled (disabled by default) |
4471 | ev_poll.c only when poll backend is enabled |
3132 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4472 | ev_epoll.c only when the epoll backend is enabled |
|
|
4473 | ev_linuxaio.c only when the linux aio backend is enabled |
3133 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4474 | ev_kqueue.c only when the kqueue backend is enabled |
3134 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4475 | ev_port.c only when the solaris port backend is enabled |
3135 | |
4476 | |
3136 | F<ev.c> includes the backend files directly when enabled, so you only need |
4477 | F<ev.c> includes the backend files directly when enabled, so you only need |
3137 | to compile this single file. |
4478 | to compile this single file. |
3138 | |
4479 | |
3139 | =head3 LIBEVENT COMPATIBILITY API |
4480 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
3165 | libev.m4 |
4506 | libev.m4 |
3166 | |
4507 | |
3167 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4508 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3168 | |
4509 | |
3169 | Libev can be configured via a variety of preprocessor symbols you have to |
4510 | Libev can be configured via a variety of preprocessor symbols you have to |
3170 | define before including any of its files. The default in the absence of |
4511 | define before including (or compiling) any of its files. The default in |
3171 | autoconf is documented for every option. |
4512 | the absence of autoconf is documented for every option. |
|
|
4513 | |
|
|
4514 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4515 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4516 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4517 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4518 | users of libev and the libev code itself must be compiled with compatible |
|
|
4519 | settings. |
3172 | |
4520 | |
3173 | =over 4 |
4521 | =over 4 |
3174 | |
4522 | |
|
|
4523 | =item EV_COMPAT3 (h) |
|
|
4524 | |
|
|
4525 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4526 | release of libev comes with wrappers for the functions and symbols that |
|
|
4527 | have been renamed between libev version 3 and 4. |
|
|
4528 | |
|
|
4529 | You can disable these wrappers (to test compatibility with future |
|
|
4530 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4531 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4532 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4533 | typedef in that case. |
|
|
4534 | |
|
|
4535 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4536 | and in some even more future version the compatibility code will be |
|
|
4537 | removed completely. |
|
|
4538 | |
3175 | =item EV_STANDALONE |
4539 | =item EV_STANDALONE (h) |
3176 | |
4540 | |
3177 | Must always be C<1> if you do not use autoconf configuration, which |
4541 | Must always be C<1> if you do not use autoconf configuration, which |
3178 | keeps libev from including F<config.h>, and it also defines dummy |
4542 | keeps libev from including F<config.h>, and it also defines dummy |
3179 | implementations for some libevent functions (such as logging, which is not |
4543 | implementations for some libevent functions (such as logging, which is not |
3180 | supported). It will also not define any of the structs usually found in |
4544 | supported). It will also not define any of the structs usually found in |
3181 | F<event.h> that are not directly supported by the libev core alone. |
4545 | F<event.h> that are not directly supported by the libev core alone. |
3182 | |
4546 | |
|
|
4547 | In standalone mode, libev will still try to automatically deduce the |
|
|
4548 | configuration, but has to be more conservative. |
|
|
4549 | |
|
|
4550 | =item EV_USE_FLOOR |
|
|
4551 | |
|
|
4552 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4553 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4554 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4555 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4556 | function is not available will fail, so the safe default is to not enable |
|
|
4557 | this. |
|
|
4558 | |
3183 | =item EV_USE_MONOTONIC |
4559 | =item EV_USE_MONOTONIC |
3184 | |
4560 | |
3185 | If defined to be C<1>, libev will try to detect the availability of the |
4561 | If defined to be C<1>, libev will try to detect the availability of the |
3186 | monotonic clock option at both compile time and runtime. Otherwise no use |
4562 | monotonic clock option at both compile time and runtime. Otherwise no |
3187 | of the monotonic clock option will be attempted. If you enable this, you |
4563 | use of the monotonic clock option will be attempted. If you enable this, |
3188 | usually have to link against librt or something similar. Enabling it when |
4564 | you usually have to link against librt or something similar. Enabling it |
3189 | the functionality isn't available is safe, though, although you have |
4565 | when the functionality isn't available is safe, though, although you have |
3190 | to make sure you link against any libraries where the C<clock_gettime> |
4566 | to make sure you link against any libraries where the C<clock_gettime> |
3191 | function is hiding in (often F<-lrt>). |
4567 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3192 | |
4568 | |
3193 | =item EV_USE_REALTIME |
4569 | =item EV_USE_REALTIME |
3194 | |
4570 | |
3195 | If defined to be C<1>, libev will try to detect the availability of the |
4571 | If defined to be C<1>, libev will try to detect the availability of the |
3196 | real-time clock option at compile time (and assume its availability at |
4572 | real-time clock option at compile time (and assume its availability |
3197 | runtime if successful). Otherwise no use of the real-time clock option will |
4573 | at runtime if successful). Otherwise no use of the real-time clock |
3198 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
4574 | option will be attempted. This effectively replaces C<gettimeofday> |
3199 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
4575 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3200 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
4576 | correctness. See the note about libraries in the description of |
|
|
4577 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
4578 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
4579 | |
|
|
4580 | =item EV_USE_CLOCK_SYSCALL |
|
|
4581 | |
|
|
4582 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
4583 | of calling the system-provided C<clock_gettime> function. This option |
|
|
4584 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
4585 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
4586 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4587 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4588 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
4589 | higher, as it simplifies linking (no need for C<-lrt>). |
3201 | |
4590 | |
3202 | =item EV_USE_NANOSLEEP |
4591 | =item EV_USE_NANOSLEEP |
3203 | |
4592 | |
3204 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
4593 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3205 | and will use it for delays. Otherwise it will use C<select ()>. |
4594 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3221 | |
4610 | |
3222 | =item EV_SELECT_USE_FD_SET |
4611 | =item EV_SELECT_USE_FD_SET |
3223 | |
4612 | |
3224 | If defined to C<1>, then the select backend will use the system C<fd_set> |
4613 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3225 | structure. This is useful if libev doesn't compile due to a missing |
4614 | structure. This is useful if libev doesn't compile due to a missing |
3226 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
4615 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3227 | exotic systems. This usually limits the range of file descriptors to some |
4616 | on exotic systems. This usually limits the range of file descriptors to |
3228 | low limit such as 1024 or might have other limitations (winsocket only |
4617 | some low limit such as 1024 or might have other limitations (winsocket |
3229 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
4618 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3230 | influence the size of the C<fd_set> used. |
4619 | configures the maximum size of the C<fd_set>. |
3231 | |
4620 | |
3232 | =item EV_SELECT_IS_WINSOCKET |
4621 | =item EV_SELECT_IS_WINSOCKET |
3233 | |
4622 | |
3234 | When defined to C<1>, the select backend will assume that |
4623 | When defined to C<1>, the select backend will assume that |
3235 | select/socket/connect etc. don't understand file descriptors but |
4624 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3237 | be used is the winsock select). This means that it will call |
4626 | be used is the winsock select). This means that it will call |
3238 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4627 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3239 | it is assumed that all these functions actually work on fds, even |
4628 | it is assumed that all these functions actually work on fds, even |
3240 | on win32. Should not be defined on non-win32 platforms. |
4629 | on win32. Should not be defined on non-win32 platforms. |
3241 | |
4630 | |
3242 | =item EV_FD_TO_WIN32_HANDLE |
4631 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3243 | |
4632 | |
3244 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4633 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3245 | file descriptors to socket handles. When not defining this symbol (the |
4634 | file descriptors to socket handles. When not defining this symbol (the |
3246 | default), then libev will call C<_get_osfhandle>, which is usually |
4635 | default), then libev will call C<_get_osfhandle>, which is usually |
3247 | correct. In some cases, programs use their own file descriptor management, |
4636 | correct. In some cases, programs use their own file descriptor management, |
3248 | in which case they can provide this function to map fds to socket handles. |
4637 | in which case they can provide this function to map fds to socket handles. |
3249 | |
4638 | |
|
|
4639 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4640 | |
|
|
4641 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4642 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4643 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4644 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4645 | |
|
|
4646 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4647 | |
|
|
4648 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4649 | macro can be used to override the C<close> function, useful to unregister |
|
|
4650 | file descriptors again. Note that the replacement function has to close |
|
|
4651 | the underlying OS handle. |
|
|
4652 | |
|
|
4653 | =item EV_USE_WSASOCKET |
|
|
4654 | |
|
|
4655 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4656 | communication socket, which works better in some environments. Otherwise, |
|
|
4657 | the normal C<socket> function will be used, which works better in other |
|
|
4658 | environments. |
|
|
4659 | |
3250 | =item EV_USE_POLL |
4660 | =item EV_USE_POLL |
3251 | |
4661 | |
3252 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4662 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3253 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4663 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3254 | takes precedence over select. |
4664 | takes precedence over select. |
… | |
… | |
3258 | If defined to be C<1>, libev will compile in support for the Linux |
4668 | If defined to be C<1>, libev will compile in support for the Linux |
3259 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4669 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3260 | otherwise another method will be used as fallback. This is the preferred |
4670 | otherwise another method will be used as fallback. This is the preferred |
3261 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4671 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
3262 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4672 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4673 | |
|
|
4674 | =item EV_USE_LINUXAIO |
|
|
4675 | |
|
|
4676 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4677 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4678 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4679 | disabled. |
3263 | |
4680 | |
3264 | =item EV_USE_KQUEUE |
4681 | =item EV_USE_KQUEUE |
3265 | |
4682 | |
3266 | If defined to be C<1>, libev will compile in support for the BSD style |
4683 | If defined to be C<1>, libev will compile in support for the BSD style |
3267 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4684 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
3289 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4706 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3290 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4707 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3291 | be detected at runtime. If undefined, it will be enabled if the headers |
4708 | be detected at runtime. If undefined, it will be enabled if the headers |
3292 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4709 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3293 | |
4710 | |
|
|
4711 | =item EV_NO_SMP |
|
|
4712 | |
|
|
4713 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4714 | between threads, that is, threads can be used, but threads never run on |
|
|
4715 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4716 | and makes libev faster. |
|
|
4717 | |
|
|
4718 | =item EV_NO_THREADS |
|
|
4719 | |
|
|
4720 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4721 | different threads (that includes signal handlers), which is a stronger |
|
|
4722 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4723 | libev faster. |
|
|
4724 | |
3294 | =item EV_ATOMIC_T |
4725 | =item EV_ATOMIC_T |
3295 | |
4726 | |
3296 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4727 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3297 | access is atomic with respect to other threads or signal contexts. No such |
4728 | access is atomic with respect to other threads or signal contexts. No |
3298 | type is easily found in the C language, so you can provide your own type |
4729 | such type is easily found in the C language, so you can provide your own |
3299 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4730 | type that you know is safe for your purposes. It is used both for signal |
3300 | as well as for signal and thread safety in C<ev_async> watchers. |
4731 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4732 | watchers. |
3301 | |
4733 | |
3302 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4734 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3303 | (from F<signal.h>), which is usually good enough on most platforms. |
4735 | (from F<signal.h>), which is usually good enough on most platforms. |
3304 | |
4736 | |
3305 | =item EV_H |
4737 | =item EV_H (h) |
3306 | |
4738 | |
3307 | The name of the F<ev.h> header file used to include it. The default if |
4739 | The name of the F<ev.h> header file used to include it. The default if |
3308 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4740 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3309 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4741 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3310 | |
4742 | |
3311 | =item EV_CONFIG_H |
4743 | =item EV_CONFIG_H (h) |
3312 | |
4744 | |
3313 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4745 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3314 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4746 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3315 | C<EV_H>, above. |
4747 | C<EV_H>, above. |
3316 | |
4748 | |
3317 | =item EV_EVENT_H |
4749 | =item EV_EVENT_H (h) |
3318 | |
4750 | |
3319 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4751 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3320 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4752 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3321 | |
4753 | |
3322 | =item EV_PROTOTYPES |
4754 | =item EV_PROTOTYPES (h) |
3323 | |
4755 | |
3324 | If defined to be C<0>, then F<ev.h> will not define any function |
4756 | If defined to be C<0>, then F<ev.h> will not define any function |
3325 | prototypes, but still define all the structs and other symbols. This is |
4757 | prototypes, but still define all the structs and other symbols. This is |
3326 | occasionally useful if you want to provide your own wrapper functions |
4758 | occasionally useful if you want to provide your own wrapper functions |
3327 | around libev functions. |
4759 | around libev functions. |
… | |
… | |
3332 | will have the C<struct ev_loop *> as first argument, and you can create |
4764 | will have the C<struct ev_loop *> as first argument, and you can create |
3333 | additional independent event loops. Otherwise there will be no support |
4765 | additional independent event loops. Otherwise there will be no support |
3334 | for multiple event loops and there is no first event loop pointer |
4766 | for multiple event loops and there is no first event loop pointer |
3335 | argument. Instead, all functions act on the single default loop. |
4767 | argument. Instead, all functions act on the single default loop. |
3336 | |
4768 | |
|
|
4769 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4770 | default loop when multiplicity is switched off - you always have to |
|
|
4771 | initialise the loop manually in this case. |
|
|
4772 | |
3337 | =item EV_MINPRI |
4773 | =item EV_MINPRI |
3338 | |
4774 | |
3339 | =item EV_MAXPRI |
4775 | =item EV_MAXPRI |
3340 | |
4776 | |
3341 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4777 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3349 | fine. |
4785 | fine. |
3350 | |
4786 | |
3351 | If your embedding application does not need any priorities, defining these |
4787 | If your embedding application does not need any priorities, defining these |
3352 | both to C<0> will save some memory and CPU. |
4788 | both to C<0> will save some memory and CPU. |
3353 | |
4789 | |
3354 | =item EV_PERIODIC_ENABLE |
4790 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4791 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4792 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3355 | |
4793 | |
3356 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4794 | If undefined or defined to be C<1> (and the platform supports it), then |
3357 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4795 | the respective watcher type is supported. If defined to be C<0>, then it |
3358 | code. |
4796 | is not. Disabling watcher types mainly saves code size. |
3359 | |
4797 | |
3360 | =item EV_IDLE_ENABLE |
4798 | =item EV_FEATURES |
3361 | |
|
|
3362 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3363 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3364 | code. |
|
|
3365 | |
|
|
3366 | =item EV_EMBED_ENABLE |
|
|
3367 | |
|
|
3368 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3369 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3370 | watcher types, which therefore must not be disabled. |
|
|
3371 | |
|
|
3372 | =item EV_STAT_ENABLE |
|
|
3373 | |
|
|
3374 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3375 | defined to be C<0>, then they are not. |
|
|
3376 | |
|
|
3377 | =item EV_FORK_ENABLE |
|
|
3378 | |
|
|
3379 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3380 | defined to be C<0>, then they are not. |
|
|
3381 | |
|
|
3382 | =item EV_ASYNC_ENABLE |
|
|
3383 | |
|
|
3384 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3385 | defined to be C<0>, then they are not. |
|
|
3386 | |
|
|
3387 | =item EV_MINIMAL |
|
|
3388 | |
4799 | |
3389 | If you need to shave off some kilobytes of code at the expense of some |
4800 | If you need to shave off some kilobytes of code at the expense of some |
3390 | speed, define this symbol to C<1>. Currently this is used to override some |
4801 | speed (but with the full API), you can define this symbol to request |
3391 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4802 | certain subsets of functionality. The default is to enable all features |
3392 | much smaller 2-heap for timer management over the default 4-heap. |
4803 | that can be enabled on the platform. |
|
|
4804 | |
|
|
4805 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4806 | with some broad features you want) and then selectively re-enable |
|
|
4807 | additional parts you want, for example if you want everything minimal, |
|
|
4808 | but multiple event loop support, async and child watchers and the poll |
|
|
4809 | backend, use this: |
|
|
4810 | |
|
|
4811 | #define EV_FEATURES 0 |
|
|
4812 | #define EV_MULTIPLICITY 1 |
|
|
4813 | #define EV_USE_POLL 1 |
|
|
4814 | #define EV_CHILD_ENABLE 1 |
|
|
4815 | #define EV_ASYNC_ENABLE 1 |
|
|
4816 | |
|
|
4817 | The actual value is a bitset, it can be a combination of the following |
|
|
4818 | values (by default, all of these are enabled): |
|
|
4819 | |
|
|
4820 | =over 4 |
|
|
4821 | |
|
|
4822 | =item C<1> - faster/larger code |
|
|
4823 | |
|
|
4824 | Use larger code to speed up some operations. |
|
|
4825 | |
|
|
4826 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4827 | code size by roughly 30% on amd64). |
|
|
4828 | |
|
|
4829 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4830 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4831 | assertions. |
|
|
4832 | |
|
|
4833 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4834 | (e.g. gcc with C<-Os>). |
|
|
4835 | |
|
|
4836 | =item C<2> - faster/larger data structures |
|
|
4837 | |
|
|
4838 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4839 | hash table sizes and so on. This will usually further increase code size |
|
|
4840 | and can additionally have an effect on the size of data structures at |
|
|
4841 | runtime. |
|
|
4842 | |
|
|
4843 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4844 | (e.g. gcc with C<-Os>). |
|
|
4845 | |
|
|
4846 | =item C<4> - full API configuration |
|
|
4847 | |
|
|
4848 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4849 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4850 | |
|
|
4851 | =item C<8> - full API |
|
|
4852 | |
|
|
4853 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4854 | details on which parts of the API are still available without this |
|
|
4855 | feature, and do not complain if this subset changes over time. |
|
|
4856 | |
|
|
4857 | =item C<16> - enable all optional watcher types |
|
|
4858 | |
|
|
4859 | Enables all optional watcher types. If you want to selectively enable |
|
|
4860 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4861 | embed, async, child...) you can enable them manually by defining |
|
|
4862 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4863 | |
|
|
4864 | =item C<32> - enable all backends |
|
|
4865 | |
|
|
4866 | This enables all backends - without this feature, you need to enable at |
|
|
4867 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4868 | |
|
|
4869 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4870 | |
|
|
4871 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4872 | default. |
|
|
4873 | |
|
|
4874 | =back |
|
|
4875 | |
|
|
4876 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4877 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4878 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4879 | watchers, timers and monotonic clock support. |
|
|
4880 | |
|
|
4881 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4882 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4883 | your program might be left out as well - a binary starting a timer and an |
|
|
4884 | I/O watcher then might come out at only 5Kb. |
|
|
4885 | |
|
|
4886 | =item EV_API_STATIC |
|
|
4887 | |
|
|
4888 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4889 | will have static linkage. This means that libev will not export any |
|
|
4890 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4891 | when you embed libev, only want to use libev functions in a single file, |
|
|
4892 | and do not want its identifiers to be visible. |
|
|
4893 | |
|
|
4894 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4895 | wants to use libev. |
|
|
4896 | |
|
|
4897 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4898 | doesn't support the required declaration syntax. |
|
|
4899 | |
|
|
4900 | =item EV_AVOID_STDIO |
|
|
4901 | |
|
|
4902 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4903 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4904 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4905 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4906 | big. |
|
|
4907 | |
|
|
4908 | Note that error messages might become less precise when this option is |
|
|
4909 | enabled. |
|
|
4910 | |
|
|
4911 | =item EV_NSIG |
|
|
4912 | |
|
|
4913 | The highest supported signal number, +1 (or, the number of |
|
|
4914 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4915 | automatically, but sometimes this fails, in which case it can be |
|
|
4916 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4917 | good for about any system in existence) can save some memory, as libev |
|
|
4918 | statically allocates some 12-24 bytes per signal number. |
3393 | |
4919 | |
3394 | =item EV_PID_HASHSIZE |
4920 | =item EV_PID_HASHSIZE |
3395 | |
4921 | |
3396 | C<ev_child> watchers use a small hash table to distribute workload by |
4922 | C<ev_child> watchers use a small hash table to distribute workload by |
3397 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4923 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3398 | than enough. If you need to manage thousands of children you might want to |
4924 | usually more than enough. If you need to manage thousands of children you |
3399 | increase this value (I<must> be a power of two). |
4925 | might want to increase this value (I<must> be a power of two). |
3400 | |
4926 | |
3401 | =item EV_INOTIFY_HASHSIZE |
4927 | =item EV_INOTIFY_HASHSIZE |
3402 | |
4928 | |
3403 | C<ev_stat> watchers use a small hash table to distribute workload by |
4929 | C<ev_stat> watchers use a small hash table to distribute workload by |
3404 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4930 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3405 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4931 | disabled), usually more than enough. If you need to manage thousands of |
3406 | watchers you might want to increase this value (I<must> be a power of |
4932 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3407 | two). |
4933 | power of two). |
3408 | |
4934 | |
3409 | =item EV_USE_4HEAP |
4935 | =item EV_USE_4HEAP |
3410 | |
4936 | |
3411 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4937 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3412 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4938 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3413 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4939 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3414 | faster performance with many (thousands) of watchers. |
4940 | faster performance with many (thousands) of watchers. |
3415 | |
4941 | |
3416 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4942 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3417 | (disabled). |
4943 | will be C<0>. |
3418 | |
4944 | |
3419 | =item EV_HEAP_CACHE_AT |
4945 | =item EV_HEAP_CACHE_AT |
3420 | |
4946 | |
3421 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4947 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3422 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4948 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3423 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4949 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3424 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4950 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3425 | but avoids random read accesses on heap changes. This improves performance |
4951 | but avoids random read accesses on heap changes. This improves performance |
3426 | noticeably with many (hundreds) of watchers. |
4952 | noticeably with many (hundreds) of watchers. |
3427 | |
4953 | |
3428 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4954 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3429 | (disabled). |
4955 | will be C<0>. |
3430 | |
4956 | |
3431 | =item EV_VERIFY |
4957 | =item EV_VERIFY |
3432 | |
4958 | |
3433 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4959 | Controls how much internal verification (see C<ev_verify ()>) will |
3434 | be done: If set to C<0>, no internal verification code will be compiled |
4960 | be done: If set to C<0>, no internal verification code will be compiled |
3435 | in. If set to C<1>, then verification code will be compiled in, but not |
4961 | in. If set to C<1>, then verification code will be compiled in, but not |
3436 | called. If set to C<2>, then the internal verification code will be |
4962 | called. If set to C<2>, then the internal verification code will be |
3437 | called once per loop, which can slow down libev. If set to C<3>, then the |
4963 | called once per loop, which can slow down libev. If set to C<3>, then the |
3438 | verification code will be called very frequently, which will slow down |
4964 | verification code will be called very frequently, which will slow down |
3439 | libev considerably. |
4965 | libev considerably. |
3440 | |
4966 | |
3441 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4967 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3442 | C<0>. |
4968 | will be C<0>. |
3443 | |
4969 | |
3444 | =item EV_COMMON |
4970 | =item EV_COMMON |
3445 | |
4971 | |
3446 | By default, all watchers have a C<void *data> member. By redefining |
4972 | By default, all watchers have a C<void *data> member. By redefining |
3447 | this macro to a something else you can include more and other types of |
4973 | this macro to something else you can include more and other types of |
3448 | members. You have to define it each time you include one of the files, |
4974 | members. You have to define it each time you include one of the files, |
3449 | though, and it must be identical each time. |
4975 | though, and it must be identical each time. |
3450 | |
4976 | |
3451 | For example, the perl EV module uses something like this: |
4977 | For example, the perl EV module uses something like this: |
3452 | |
4978 | |
… | |
… | |
3505 | file. |
5031 | file. |
3506 | |
5032 | |
3507 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
5033 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3508 | that everybody includes and which overrides some configure choices: |
5034 | that everybody includes and which overrides some configure choices: |
3509 | |
5035 | |
3510 | #define EV_MINIMAL 1 |
5036 | #define EV_FEATURES 8 |
3511 | #define EV_USE_POLL 0 |
5037 | #define EV_USE_SELECT 1 |
3512 | #define EV_MULTIPLICITY 0 |
|
|
3513 | #define EV_PERIODIC_ENABLE 0 |
5038 | #define EV_PREPARE_ENABLE 1 |
|
|
5039 | #define EV_IDLE_ENABLE 1 |
3514 | #define EV_STAT_ENABLE 0 |
5040 | #define EV_SIGNAL_ENABLE 1 |
3515 | #define EV_FORK_ENABLE 0 |
5041 | #define EV_CHILD_ENABLE 1 |
|
|
5042 | #define EV_USE_STDEXCEPT 0 |
3516 | #define EV_CONFIG_H <config.h> |
5043 | #define EV_CONFIG_H <config.h> |
3517 | #define EV_MINPRI 0 |
|
|
3518 | #define EV_MAXPRI 0 |
|
|
3519 | |
5044 | |
3520 | #include "ev++.h" |
5045 | #include "ev++.h" |
3521 | |
5046 | |
3522 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
5047 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3523 | |
5048 | |
3524 | #include "ev_cpp.h" |
5049 | #include "ev_cpp.h" |
3525 | #include "ev.c" |
5050 | #include "ev.c" |
3526 | |
5051 | |
3527 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
5052 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3528 | |
5053 | |
3529 | =head2 THREADS AND COROUTINES |
5054 | =head2 THREADS AND COROUTINES |
3530 | |
5055 | |
3531 | =head3 THREADS |
5056 | =head3 THREADS |
3532 | |
5057 | |
… | |
… | |
3583 | default loop and triggering an C<ev_async> watcher from the default loop |
5108 | default loop and triggering an C<ev_async> watcher from the default loop |
3584 | watcher callback into the event loop interested in the signal. |
5109 | watcher callback into the event loop interested in the signal. |
3585 | |
5110 | |
3586 | =back |
5111 | =back |
3587 | |
5112 | |
|
|
5113 | See also L</THREAD LOCKING EXAMPLE>. |
|
|
5114 | |
3588 | =head3 COROUTINES |
5115 | =head3 COROUTINES |
3589 | |
5116 | |
3590 | Libev is very accommodating to coroutines ("cooperative threads"): |
5117 | Libev is very accommodating to coroutines ("cooperative threads"): |
3591 | libev fully supports nesting calls to its functions from different |
5118 | libev fully supports nesting calls to its functions from different |
3592 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
5119 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3593 | different coroutines, and switch freely between both coroutines running the |
5120 | different coroutines, and switch freely between both coroutines running |
3594 | loop, as long as you don't confuse yourself). The only exception is that |
5121 | the loop, as long as you don't confuse yourself). The only exception is |
3595 | you must not do this from C<ev_periodic> reschedule callbacks. |
5122 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3596 | |
5123 | |
3597 | Care has been taken to ensure that libev does not keep local state inside |
5124 | Care has been taken to ensure that libev does not keep local state inside |
3598 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
5125 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3599 | they do not call any callbacks. |
5126 | they do not call any callbacks. |
3600 | |
5127 | |
3601 | =head2 COMPILER WARNINGS |
5128 | =head2 COMPILER WARNINGS |
3602 | |
5129 | |
3603 | Depending on your compiler and compiler settings, you might get no or a |
5130 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
3614 | maintainable. |
5141 | maintainable. |
3615 | |
5142 | |
3616 | And of course, some compiler warnings are just plain stupid, or simply |
5143 | And of course, some compiler warnings are just plain stupid, or simply |
3617 | wrong (because they don't actually warn about the condition their message |
5144 | wrong (because they don't actually warn about the condition their message |
3618 | seems to warn about). For example, certain older gcc versions had some |
5145 | seems to warn about). For example, certain older gcc versions had some |
3619 | warnings that resulted an extreme number of false positives. These have |
5146 | warnings that resulted in an extreme number of false positives. These have |
3620 | been fixed, but some people still insist on making code warn-free with |
5147 | been fixed, but some people still insist on making code warn-free with |
3621 | such buggy versions. |
5148 | such buggy versions. |
3622 | |
5149 | |
3623 | While libev is written to generate as few warnings as possible, |
5150 | While libev is written to generate as few warnings as possible, |
3624 | "warn-free" code is not a goal, and it is recommended not to build libev |
5151 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3660 | I suggest using suppression lists. |
5187 | I suggest using suppression lists. |
3661 | |
5188 | |
3662 | |
5189 | |
3663 | =head1 PORTABILITY NOTES |
5190 | =head1 PORTABILITY NOTES |
3664 | |
5191 | |
|
|
5192 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
5193 | |
|
|
5194 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5195 | interfaces but I<disables> them by default. |
|
|
5196 | |
|
|
5197 | That means that libev compiled in the default environment doesn't support |
|
|
5198 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
5199 | |
|
|
5200 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5201 | by enabling the large file API, which makes them incompatible with the |
|
|
5202 | standard libev compiled for their system. |
|
|
5203 | |
|
|
5204 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5205 | suddenly make it incompatible to the default compile time environment, |
|
|
5206 | i.e. all programs not using special compile switches. |
|
|
5207 | |
|
|
5208 | =head2 OS/X AND DARWIN BUGS |
|
|
5209 | |
|
|
5210 | The whole thing is a bug if you ask me - basically any system interface |
|
|
5211 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5212 | OpenGL drivers. |
|
|
5213 | |
|
|
5214 | =head3 C<kqueue> is buggy |
|
|
5215 | |
|
|
5216 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5217 | only sockets, many support pipes. |
|
|
5218 | |
|
|
5219 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5220 | rotten platform, but of course you can still ask for it when creating a |
|
|
5221 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5222 | probably going to work well. |
|
|
5223 | |
|
|
5224 | =head3 C<poll> is buggy |
|
|
5225 | |
|
|
5226 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5227 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5228 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5229 | |
|
|
5230 | Libev tries to work around this by not using C<poll> by default on |
|
|
5231 | this rotten platform, but of course you can still ask for it when creating |
|
|
5232 | a loop. |
|
|
5233 | |
|
|
5234 | =head3 C<select> is buggy |
|
|
5235 | |
|
|
5236 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5237 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5238 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5239 | you use more. |
|
|
5240 | |
|
|
5241 | There is an undocumented "workaround" for this - defining |
|
|
5242 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5243 | work on OS/X. |
|
|
5244 | |
|
|
5245 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5246 | |
|
|
5247 | =head3 C<errno> reentrancy |
|
|
5248 | |
|
|
5249 | The default compile environment on Solaris is unfortunately so |
|
|
5250 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5251 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5252 | defined by default. A valid, if stupid, implementation choice. |
|
|
5253 | |
|
|
5254 | If you want to use libev in threaded environments you have to make sure |
|
|
5255 | it's compiled with C<_REENTRANT> defined. |
|
|
5256 | |
|
|
5257 | =head3 Event port backend |
|
|
5258 | |
|
|
5259 | The scalable event interface for Solaris is called "event |
|
|
5260 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5261 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5262 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5263 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5264 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5265 | great. |
|
|
5266 | |
|
|
5267 | If you can't get it to work, you can try running the program by setting |
|
|
5268 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5269 | C<select> backends. |
|
|
5270 | |
|
|
5271 | =head2 AIX POLL BUG |
|
|
5272 | |
|
|
5273 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5274 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5275 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5276 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5277 | |
3665 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5278 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5279 | |
|
|
5280 | =head3 General issues |
3666 | |
5281 | |
3667 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5282 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3668 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5283 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3669 | model. Libev still offers limited functionality on this platform in |
5284 | model. Libev still offers limited functionality on this platform in |
3670 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5285 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3671 | descriptors. This only applies when using Win32 natively, not when using |
5286 | descriptors. This only applies when using Win32 natively, not when using |
3672 | e.g. cygwin. |
5287 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5288 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5289 | environment. |
3673 | |
5290 | |
3674 | Lifting these limitations would basically require the full |
5291 | Lifting these limitations would basically require the full |
3675 | re-implementation of the I/O system. If you are into these kinds of |
5292 | re-implementation of the I/O system. If you are into this kind of thing, |
3676 | things, then note that glib does exactly that for you in a very portable |
5293 | then note that glib does exactly that for you in a very portable way (note |
3677 | way (note also that glib is the slowest event library known to man). |
5294 | also that glib is the slowest event library known to man). |
3678 | |
5295 | |
3679 | There is no supported compilation method available on windows except |
5296 | There is no supported compilation method available on windows except |
3680 | embedding it into other applications. |
5297 | embedding it into other applications. |
|
|
5298 | |
|
|
5299 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
5300 | tries its best, but under most conditions, signals will simply not work. |
3681 | |
5301 | |
3682 | Not a libev limitation but worth mentioning: windows apparently doesn't |
5302 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3683 | accept large writes: instead of resulting in a partial write, windows will |
5303 | accept large writes: instead of resulting in a partial write, windows will |
3684 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
5304 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3685 | so make sure you only write small amounts into your sockets (less than a |
5305 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3690 | the abysmal performance of winsockets, using a large number of sockets |
5310 | the abysmal performance of winsockets, using a large number of sockets |
3691 | is not recommended (and not reasonable). If your program needs to use |
5311 | is not recommended (and not reasonable). If your program needs to use |
3692 | more than a hundred or so sockets, then likely it needs to use a totally |
5312 | more than a hundred or so sockets, then likely it needs to use a totally |
3693 | different implementation for windows, as libev offers the POSIX readiness |
5313 | different implementation for windows, as libev offers the POSIX readiness |
3694 | notification model, which cannot be implemented efficiently on windows |
5314 | notification model, which cannot be implemented efficiently on windows |
3695 | (Microsoft monopoly games). |
5315 | (due to Microsoft monopoly games). |
3696 | |
5316 | |
3697 | A typical way to use libev under windows is to embed it (see the embedding |
5317 | A typical way to use libev under windows is to embed it (see the embedding |
3698 | section for details) and use the following F<evwrap.h> header file instead |
5318 | section for details) and use the following F<evwrap.h> header file instead |
3699 | of F<ev.h>: |
5319 | of F<ev.h>: |
3700 | |
5320 | |
… | |
… | |
3707 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
5327 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3708 | |
5328 | |
3709 | #include "evwrap.h" |
5329 | #include "evwrap.h" |
3710 | #include "ev.c" |
5330 | #include "ev.c" |
3711 | |
5331 | |
3712 | =over 4 |
|
|
3713 | |
|
|
3714 | =item The winsocket select function |
5332 | =head3 The winsocket C<select> function |
3715 | |
5333 | |
3716 | The winsocket C<select> function doesn't follow POSIX in that it |
5334 | The winsocket C<select> function doesn't follow POSIX in that it |
3717 | requires socket I<handles> and not socket I<file descriptors> (it is |
5335 | requires socket I<handles> and not socket I<file descriptors> (it is |
3718 | also extremely buggy). This makes select very inefficient, and also |
5336 | also extremely buggy). This makes select very inefficient, and also |
3719 | requires a mapping from file descriptors to socket handles (the Microsoft |
5337 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3728 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5346 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3729 | |
5347 | |
3730 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5348 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3731 | complexity in the O(n²) range when using win32. |
5349 | complexity in the O(n²) range when using win32. |
3732 | |
5350 | |
3733 | =item Limited number of file descriptors |
5351 | =head3 Limited number of file descriptors |
3734 | |
5352 | |
3735 | Windows has numerous arbitrary (and low) limits on things. |
5353 | Windows has numerous arbitrary (and low) limits on things. |
3736 | |
5354 | |
3737 | Early versions of winsocket's select only supported waiting for a maximum |
5355 | Early versions of winsocket's select only supported waiting for a maximum |
3738 | of C<64> handles (probably owning to the fact that all windows kernels |
5356 | of C<64> handles (probably owning to the fact that all windows kernels |
3739 | can only wait for C<64> things at the same time internally; Microsoft |
5357 | can only wait for C<64> things at the same time internally; Microsoft |
3740 | recommends spawning a chain of threads and wait for 63 handles and the |
5358 | recommends spawning a chain of threads and wait for 63 handles and the |
3741 | previous thread in each. Great). |
5359 | previous thread in each. Sounds great!). |
3742 | |
5360 | |
3743 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
5361 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3744 | to some high number (e.g. C<2048>) before compiling the winsocket select |
5362 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3745 | call (which might be in libev or elsewhere, for example, perl does its own |
5363 | call (which might be in libev or elsewhere, for example, perl and many |
3746 | select emulation on windows). |
5364 | other interpreters do their own select emulation on windows). |
3747 | |
5365 | |
3748 | Another limit is the number of file descriptors in the Microsoft runtime |
5366 | Another limit is the number of file descriptors in the Microsoft runtime |
3749 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
5367 | libraries, which by default is C<64> (there must be a hidden I<64> |
3750 | or something like this inside Microsoft). You can increase this by calling |
5368 | fetish or something like this inside Microsoft). You can increase this |
3751 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
5369 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3752 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
5370 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3753 | libraries. |
|
|
3754 | |
|
|
3755 | This might get you to about C<512> or C<2048> sockets (depending on |
5371 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3756 | windows version and/or the phase of the moon). To get more, you need to |
5372 | (depending on windows version and/or the phase of the moon). To get more, |
3757 | wrap all I/O functions and provide your own fd management, but the cost of |
5373 | you need to wrap all I/O functions and provide your own fd management, but |
3758 | calling select (O(n²)) will likely make this unworkable. |
5374 | the cost of calling select (O(n²)) will likely make this unworkable. |
3759 | |
|
|
3760 | =back |
|
|
3761 | |
5375 | |
3762 | =head2 PORTABILITY REQUIREMENTS |
5376 | =head2 PORTABILITY REQUIREMENTS |
3763 | |
5377 | |
3764 | In addition to a working ISO-C implementation and of course the |
5378 | In addition to a working ISO-C implementation and of course the |
3765 | backend-specific APIs, libev relies on a few additional extensions: |
5379 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
3772 | Libev assumes not only that all watcher pointers have the same internal |
5386 | Libev assumes not only that all watcher pointers have the same internal |
3773 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5387 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
3774 | assumes that the same (machine) code can be used to call any watcher |
5388 | assumes that the same (machine) code can be used to call any watcher |
3775 | callback: The watcher callbacks have different type signatures, but libev |
5389 | callback: The watcher callbacks have different type signatures, but libev |
3776 | calls them using an C<ev_watcher *> internally. |
5390 | calls them using an C<ev_watcher *> internally. |
|
|
5391 | |
|
|
5392 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5393 | |
|
|
5394 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5395 | relies on this setting pointers and integers to null. |
|
|
5396 | |
|
|
5397 | =item pointer accesses must be thread-atomic |
|
|
5398 | |
|
|
5399 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5400 | writable in one piece - this is the case on all current architectures. |
3777 | |
5401 | |
3778 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5402 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3779 | |
5403 | |
3780 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5404 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3781 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5405 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
3790 | thread" or will block signals process-wide, both behaviours would |
5414 | thread" or will block signals process-wide, both behaviours would |
3791 | be compatible with libev. Interaction between C<sigprocmask> and |
5415 | be compatible with libev. Interaction between C<sigprocmask> and |
3792 | C<pthread_sigmask> could complicate things, however. |
5416 | C<pthread_sigmask> could complicate things, however. |
3793 | |
5417 | |
3794 | The most portable way to handle signals is to block signals in all threads |
5418 | The most portable way to handle signals is to block signals in all threads |
3795 | except the initial one, and run the default loop in the initial thread as |
5419 | except the initial one, and run the signal handling loop in the initial |
3796 | well. |
5420 | thread as well. |
3797 | |
5421 | |
3798 | =item C<long> must be large enough for common memory allocation sizes |
5422 | =item C<long> must be large enough for common memory allocation sizes |
3799 | |
5423 | |
3800 | To improve portability and simplify its API, libev uses C<long> internally |
5424 | To improve portability and simplify its API, libev uses C<long> internally |
3801 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5425 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
3804 | watchers. |
5428 | watchers. |
3805 | |
5429 | |
3806 | =item C<double> must hold a time value in seconds with enough accuracy |
5430 | =item C<double> must hold a time value in seconds with enough accuracy |
3807 | |
5431 | |
3808 | The type C<double> is used to represent timestamps. It is required to |
5432 | The type C<double> is used to represent timestamps. It is required to |
3809 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5433 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3810 | enough for at least into the year 4000. This requirement is fulfilled by |
5434 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5435 | (the design goal for libev). This requirement is overfulfilled by |
3811 | implementations implementing IEEE 754 (basically all existing ones). |
5436 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5437 | |
|
|
5438 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5439 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5440 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5441 | something like that, just kidding). |
3812 | |
5442 | |
3813 | =back |
5443 | =back |
3814 | |
5444 | |
3815 | If you know of other additional requirements drop me a note. |
5445 | If you know of other additional requirements drop me a note. |
3816 | |
5446 | |
… | |
… | |
3878 | =item Processing ev_async_send: O(number_of_async_watchers) |
5508 | =item Processing ev_async_send: O(number_of_async_watchers) |
3879 | |
5509 | |
3880 | =item Processing signals: O(max_signal_number) |
5510 | =item Processing signals: O(max_signal_number) |
3881 | |
5511 | |
3882 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5512 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
3883 | calls in the current loop iteration. Checking for async and signal events |
5513 | calls in the current loop iteration and the loop is currently |
|
|
5514 | blocked. Checking for async and signal events involves iterating over all |
3884 | involves iterating over all running async watchers or all signal numbers. |
5515 | running async watchers or all signal numbers. |
3885 | |
5516 | |
3886 | =back |
5517 | =back |
3887 | |
5518 | |
3888 | |
5519 | |
|
|
5520 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5521 | |
|
|
5522 | The major version 4 introduced some incompatible changes to the API. |
|
|
5523 | |
|
|
5524 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5525 | for all changes, so most programs should still compile. The compatibility |
|
|
5526 | layer might be removed in later versions of libev, so better update to the |
|
|
5527 | new API early than late. |
|
|
5528 | |
|
|
5529 | =over 4 |
|
|
5530 | |
|
|
5531 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5532 | |
|
|
5533 | The backward compatibility mechanism can be controlled by |
|
|
5534 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5535 | section. |
|
|
5536 | |
|
|
5537 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5538 | |
|
|
5539 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5540 | |
|
|
5541 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5542 | ev_loop_fork (EV_DEFAULT); |
|
|
5543 | |
|
|
5544 | =item function/symbol renames |
|
|
5545 | |
|
|
5546 | A number of functions and symbols have been renamed: |
|
|
5547 | |
|
|
5548 | ev_loop => ev_run |
|
|
5549 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5550 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5551 | |
|
|
5552 | ev_unloop => ev_break |
|
|
5553 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5554 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5555 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5556 | |
|
|
5557 | EV_TIMEOUT => EV_TIMER |
|
|
5558 | |
|
|
5559 | ev_loop_count => ev_iteration |
|
|
5560 | ev_loop_depth => ev_depth |
|
|
5561 | ev_loop_verify => ev_verify |
|
|
5562 | |
|
|
5563 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5564 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5565 | associated constants have been renamed to not collide with the C<struct |
|
|
5566 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5567 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5568 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5569 | typedef. |
|
|
5570 | |
|
|
5571 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5572 | |
|
|
5573 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5574 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5575 | and work, but the library code will of course be larger. |
|
|
5576 | |
|
|
5577 | =back |
|
|
5578 | |
|
|
5579 | |
|
|
5580 | =head1 GLOSSARY |
|
|
5581 | |
|
|
5582 | =over 4 |
|
|
5583 | |
|
|
5584 | =item active |
|
|
5585 | |
|
|
5586 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5587 | See L</WATCHER STATES> for details. |
|
|
5588 | |
|
|
5589 | =item application |
|
|
5590 | |
|
|
5591 | In this document, an application is whatever is using libev. |
|
|
5592 | |
|
|
5593 | =item backend |
|
|
5594 | |
|
|
5595 | The part of the code dealing with the operating system interfaces. |
|
|
5596 | |
|
|
5597 | =item callback |
|
|
5598 | |
|
|
5599 | The address of a function that is called when some event has been |
|
|
5600 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5601 | received the event, and the actual event bitset. |
|
|
5602 | |
|
|
5603 | =item callback/watcher invocation |
|
|
5604 | |
|
|
5605 | The act of calling the callback associated with a watcher. |
|
|
5606 | |
|
|
5607 | =item event |
|
|
5608 | |
|
|
5609 | A change of state of some external event, such as data now being available |
|
|
5610 | for reading on a file descriptor, time having passed or simply not having |
|
|
5611 | any other events happening anymore. |
|
|
5612 | |
|
|
5613 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5614 | C<EV_TIMER>). |
|
|
5615 | |
|
|
5616 | =item event library |
|
|
5617 | |
|
|
5618 | A software package implementing an event model and loop. |
|
|
5619 | |
|
|
5620 | =item event loop |
|
|
5621 | |
|
|
5622 | An entity that handles and processes external events and converts them |
|
|
5623 | into callback invocations. |
|
|
5624 | |
|
|
5625 | =item event model |
|
|
5626 | |
|
|
5627 | The model used to describe how an event loop handles and processes |
|
|
5628 | watchers and events. |
|
|
5629 | |
|
|
5630 | =item pending |
|
|
5631 | |
|
|
5632 | A watcher is pending as soon as the corresponding event has been |
|
|
5633 | detected. See L</WATCHER STATES> for details. |
|
|
5634 | |
|
|
5635 | =item real time |
|
|
5636 | |
|
|
5637 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5638 | |
|
|
5639 | =item wall-clock time |
|
|
5640 | |
|
|
5641 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5642 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5643 | clock. |
|
|
5644 | |
|
|
5645 | =item watcher |
|
|
5646 | |
|
|
5647 | A data structure that describes interest in certain events. Watchers need |
|
|
5648 | to be started (attached to an event loop) before they can receive events. |
|
|
5649 | |
|
|
5650 | =back |
|
|
5651 | |
3889 | =head1 AUTHOR |
5652 | =head1 AUTHOR |
3890 | |
5653 | |
3891 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5654 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5655 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
3892 | |
5656 | |