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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
52 | |
54 | |
53 | // initialise a timer watcher, then start it |
55 | // initialise a timer watcher, then start it |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familiarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
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84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | 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 |
131 | 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 |
132 | 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 |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
119 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
121 | |
137 | |
122 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
123 | |
139 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
141 | and internal errors (bugs). |
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149 | |
165 | |
150 | =item ev_tstamp ev_time () |
166 | =item ev_tstamp ev_time () |
151 | |
167 | |
152 | Returns the current time as libev would use it. Please note that the |
168 | 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 |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
170 | you actually want to know. Also interesting is the combination of |
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171 | C<ev_update_now> and C<ev_now>. |
155 | |
172 | |
156 | =item ev_sleep (ev_tstamp interval) |
173 | =item ev_sleep (ev_tstamp interval) |
157 | |
174 | |
158 | Sleep for the given interval: The current thread will be blocked until |
175 | Sleep for the given interval: The current thread will be blocked until |
159 | either it is interrupted or the given time interval has passed. Basically |
176 | either it is interrupted or the given time interval has passed. Basically |
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176 | as this indicates an incompatible change. Minor versions are usually |
193 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
194 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
195 | not a problem. |
179 | |
196 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
198 | version (note, however, that this will not detect other ABI mismatches, |
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199 | such as LFS or reentrancy). |
182 | |
200 | |
183 | assert (("libev version mismatch", |
201 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
202 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
203 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
204 | |
187 | =item unsigned int ev_supported_backends () |
205 | =item unsigned int ev_supported_backends () |
188 | |
206 | |
189 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
207 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
190 | value) compiled into this binary of libev (independent of their |
208 | value) compiled into this binary of libev (independent of their |
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192 | a description of the set values. |
210 | a description of the set values. |
193 | |
211 | |
194 | Example: make sure we have the epoll method, because yeah this is cool and |
212 | Example: make sure we have the epoll method, because yeah this is cool and |
195 | a must have and can we have a torrent of it please!!!11 |
213 | a must have and can we have a torrent of it please!!!11 |
196 | |
214 | |
197 | assert (("sorry, no epoll, no sex", |
215 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
216 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
217 | |
200 | =item unsigned int ev_recommended_backends () |
218 | =item unsigned int ev_recommended_backends () |
201 | |
219 | |
202 | Return the set of all backends compiled into this binary of libev and also |
220 | 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 |
221 | also recommended for this platform, meaning it will work for most file |
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222 | 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 |
223 | 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 |
224 | 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 |
225 | 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. |
226 | probe for if you specify no backends explicitly. |
208 | |
227 | |
209 | =item unsigned int ev_embeddable_backends () |
228 | =item unsigned int ev_embeddable_backends () |
210 | |
229 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
230 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
231 | 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 |
232 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
233 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
235 | |
217 | See the description of C<ev_embed> watchers for more info. |
236 | See the description of C<ev_embed> watchers for more info. |
218 | |
237 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
239 | |
221 | Sets the allocation function to use (the prototype is similar - the |
240 | 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 |
241 | 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 |
242 | 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 |
243 | when memory needs to be allocated (C<size != 0>), the library might abort |
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250 | } |
269 | } |
251 | |
270 | |
252 | ... |
271 | ... |
253 | ev_set_allocator (persistent_realloc); |
272 | ev_set_allocator (persistent_realloc); |
254 | |
273 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
275 | |
257 | Set the callback function to call on a retryable system call error (such |
276 | 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 |
277 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
278 | 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 |
279 | callback is set, then libev will expect it to remedy the situation, no |
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274 | ... |
293 | ... |
275 | ev_set_syserr_cb (fatal_error); |
294 | ev_set_syserr_cb (fatal_error); |
276 | |
295 | |
277 | =back |
296 | =back |
278 | |
297 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
298 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
299 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
282 | types of such loops, the I<default> loop, which supports signals and child |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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303 | |
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304 | The library knows two types of such loops, the I<default> loop, which |
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305 | supports signals and child events, and dynamically created event loops |
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306 | which do not. |
284 | |
307 | |
285 | =over 4 |
308 | =over 4 |
286 | |
309 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
311 | |
289 | This will initialise the default event loop if it hasn't been initialised |
312 | This returns the "default" event loop object, which is what you should |
290 | yet and return it. If the default loop could not be initialised, returns |
313 | normally use when you just need "the event loop". Event loop objects and |
291 | false. If it already was initialised it simply returns it (and ignores the |
314 | the C<flags> parameter are described in more detail in the entry for |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
315 | C<ev_loop_new>. |
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316 | |
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317 | If the default loop is already initialised then this function simply |
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318 | returns it (and ignores the flags. If that is troubling you, check |
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319 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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320 | flags, which should almost always be C<0>, unless the caller is also the |
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321 | one calling C<ev_run> or otherwise qualifies as "the main program". |
293 | |
322 | |
294 | If you don't know what event loop to use, use the one returned from this |
323 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
324 | function (or via the C<EV_DEFAULT> macro). |
296 | |
325 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
326 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
327 | from multiple threads, you have to employ some kind of mutex (note also |
299 | as loops cannot bes hared easily between threads anyway). |
328 | that this case is unlikely, as loops cannot be shared easily between |
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329 | threads anyway). |
300 | |
330 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
331 | The default loop is the only loop that can handle C<ev_child> watchers, |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
332 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
333 | a problem for your application you can either create a dynamic loop with |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
334 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
335 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
306 | C<ev_default_init>. |
336 | |
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337 | Example: This is the most typical usage. |
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338 | |
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339 | if (!ev_default_loop (0)) |
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340 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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341 | |
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342 | Example: Restrict libev to the select and poll backends, and do not allow |
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343 | environment settings to be taken into account: |
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344 | |
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345 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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346 | |
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347 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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348 | |
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349 | This will create and initialise a new event loop object. If the loop |
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350 | could not be initialised, returns false. |
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351 | |
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352 | Note that this function I<is> thread-safe, and one common way to use |
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353 | libev with threads is indeed to create one loop per thread, and using the |
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354 | default loop in the "main" or "initial" thread. |
307 | |
355 | |
308 | The flags argument can be used to specify special behaviour or specific |
356 | The flags argument can be used to specify special behaviour or specific |
309 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
357 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
310 | |
358 | |
311 | The following flags are supported: |
359 | The following flags are supported: |
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326 | useful to try out specific backends to test their performance, or to work |
374 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
375 | around bugs. |
328 | |
376 | |
329 | =item C<EVFLAG_FORKCHECK> |
377 | =item C<EVFLAG_FORKCHECK> |
330 | |
378 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
379 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
332 | a fork, you can also make libev check for a fork in each iteration by |
380 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
381 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
382 | This works by calling C<getpid ()> on every iteration of the loop, |
336 | and thus this might slow down your event loop if you do a lot of loop |
383 | and thus this might slow down your event loop if you do a lot of loop |
337 | iterations and little real work, but is usually not noticeable (on my |
384 | iterations and little real work, but is usually not noticeable (on my |
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
385 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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344 | flag. |
391 | flag. |
345 | |
392 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
393 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
394 | environment variable. |
348 | |
395 | |
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396 | =item C<EVFLAG_NOINOTIFY> |
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397 | |
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398 | When this flag is specified, then libev will not attempt to use the |
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399 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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400 | testing, this flag can be useful to conserve inotify file descriptors, as |
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401 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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402 | |
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403 | =item C<EVFLAG_SIGNALFD> |
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404 | |
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405 | When this flag is specified, then libev will attempt to use the |
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406 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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407 | delivers signals synchronously, which makes it both faster and might make |
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408 | it possible to get the queued signal data. It can also simplify signal |
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409 | handling with threads, as long as you properly block signals in your |
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410 | threads that are not interested in handling them. |
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411 | |
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412 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
413 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
414 | example) that can't properly initialise their signal masks. |
|
|
415 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
416 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
417 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
418 | This is your standard select(2) backend. Not I<completely> standard, as |
352 | libev tries to roll its own fd_set with no limits on the number of fds, |
419 | libev tries to roll its own fd_set with no limits on the number of fds, |
353 | but if that fails, expect a fairly low limit on the number of fds when |
420 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
426 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
427 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
428 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
429 | readiness notifications you get per iteration. |
363 | |
430 | |
|
|
431 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
432 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
433 | C<exceptfds> set on that platform). |
|
|
434 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
435 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
436 | |
366 | And this is your standard poll(2) backend. It's more complicated |
437 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
438 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
439 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
440 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
441 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
442 | performance tips. |
372 | |
443 | |
|
|
444 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
445 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
446 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
447 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
|
448 | |
|
|
449 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
450 | kernels). |
374 | |
451 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
452 | For few fds, this backend is a bit little slower than poll and select, |
376 | but it scales phenomenally better. While poll and select usually scale |
453 | but it scales phenomenally better. While poll and select usually scale |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
454 | like O(total_fds) where n is the total number of fds (or the highest fd), |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
455 | epoll scales either O(1) or O(active_fds). |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
456 | |
380 | cases and requiring a system call per fd change, no fork support and bad |
457 | The epoll mechanism deserves honorable mention as the most misdesigned |
381 | support for dup. |
458 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
459 | dropping file descriptors, requiring a system call per change per file |
|
|
460 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
461 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
462 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
463 | take considerable time (one syscall per file descriptor) and is of course |
|
|
464 | hard to detect. |
|
|
465 | |
|
|
466 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
467 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
468 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
469 | even remove them from the set) than registered in the set (especially |
|
|
470 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
471 | employing an additional generation counter and comparing that against the |
|
|
472 | events to filter out spurious ones, recreating the set when required. Last |
|
|
473 | not least, it also refuses to work with some file descriptors which work |
|
|
474 | perfectly fine with C<select> (files, many character devices...). |
382 | |
475 | |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
476 | While stopping, setting and starting an I/O watcher in the same iteration |
384 | will result in some caching, there is still a system call per such incident |
477 | will result in some caching, there is still a system call per such |
385 | (because the fd could point to a different file description now), so its |
478 | incident (because the same I<file descriptor> could point to a different |
386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
479 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
387 | very well if you register events for both fds. |
480 | file descriptors might not work very well if you register events for both |
388 | |
481 | file descriptors. |
389 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
391 | (or space) is available. |
|
|
392 | |
482 | |
393 | Best performance from this backend is achieved by not unregistering all |
483 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
484 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
485 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
486 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
487 | extra overhead. A fork can both result in spurious notifications as well |
|
|
488 | as in libev having to destroy and recreate the epoll object, which can |
|
|
489 | take considerable time and thus should be avoided. |
|
|
490 | |
|
|
491 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
492 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
493 | the usage. So sad. |
396 | |
494 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
495 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
496 | all kernel versions tested so far. |
|
|
497 | |
|
|
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
499 | C<EVBACKEND_POLL>. |
399 | |
500 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
501 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
502 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
503 | Kqueue deserves special mention, as at the time of this writing, it |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
504 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
404 | with anything but sockets and pipes, except on Darwin, where of course |
505 | with anything but sockets and pipes, except on Darwin, where of course |
405 | it's completely useless). For this reason it's not being "auto-detected" |
506 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
507 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
508 | without API changes to existing programs. For this reason it's not being |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
509 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
510 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
408 | system like NetBSD. |
511 | system like NetBSD. |
409 | |
512 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
513 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
514 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
413 | |
516 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
517 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
518 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
519 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
520 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
521 | two event changes per incident. Support for C<fork ()> is very bad (but |
419 | drops fds silently in similarly hard-to-detect cases. |
522 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
523 | cases |
420 | |
524 | |
421 | This backend usually performs well under most conditions. |
525 | This backend usually performs well under most conditions. |
422 | |
526 | |
423 | While nominally embeddable in other event loops, this doesn't work |
527 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
528 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
529 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
530 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
531 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
428 | sockets. |
532 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
533 | |
|
|
534 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
535 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
536 | C<NOTE_EOF>. |
429 | |
537 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
538 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
539 | |
432 | This is not implemented yet (and might never be, unless you send me an |
540 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
541 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
554 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
555 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
556 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
557 | might perform better. |
450 | |
558 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
559 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
560 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
561 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
562 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
563 | |
|
|
564 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
565 | C<EVBACKEND_POLL>. |
454 | |
566 | |
455 | =item C<EVBACKEND_ALL> |
567 | =item C<EVBACKEND_ALL> |
456 | |
568 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
569 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
570 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
460 | |
572 | |
461 | It is definitely not recommended to use this flag. |
573 | It is definitely not recommended to use this flag. |
462 | |
574 | |
463 | =back |
575 | =back |
464 | |
576 | |
465 | If one or more of these are or'ed into the flags value, then only these |
577 | If one or more of the backend flags are or'ed into the flags value, |
466 | backends will be tried (in the reverse order as listed here). If none are |
578 | then only these backends will be tried (in the reverse order as listed |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
579 | here). If none are specified, all backends in C<ev_recommended_backends |
468 | |
580 | ()> will be tried. |
469 | The most typical usage is like this: |
|
|
470 | |
|
|
471 | if (!ev_default_loop (0)) |
|
|
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
473 | |
|
|
474 | Restrict libev to the select and poll backends, and do not allow |
|
|
475 | environment settings to be taken into account: |
|
|
476 | |
|
|
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
478 | |
|
|
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
480 | available (warning, breaks stuff, best use only with your own private |
|
|
481 | event loop and only if you know the OS supports your types of fds): |
|
|
482 | |
|
|
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
484 | |
|
|
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
486 | |
|
|
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
488 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
489 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
491 | |
|
|
492 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
493 | libev with threads is indeed to create one loop per thread, and using the |
|
|
494 | default loop in the "main" or "initial" thread. |
|
|
495 | |
581 | |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
582 | Example: Try to create a event loop that uses epoll and nothing else. |
497 | |
583 | |
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
584 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
499 | if (!epoller) |
585 | if (!epoller) |
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
586 | fatal ("no epoll found here, maybe it hides under your chair"); |
501 | |
587 | |
|
|
588 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
589 | used if available. |
|
|
590 | |
|
|
591 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
592 | |
502 | =item ev_default_destroy () |
593 | =item ev_loop_destroy (loop) |
503 | |
594 | |
504 | Destroys the default loop again (frees all memory and kernel state |
595 | Destroys an event loop object (frees all memory and kernel state |
505 | etc.). None of the active event watchers will be stopped in the normal |
596 | etc.). None of the active event watchers will be stopped in the normal |
506 | sense, so e.g. C<ev_is_active> might still return true. It is your |
597 | sense, so e.g. C<ev_is_active> might still return true. It is your |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
598 | responsibility to either stop all watchers cleanly yourself I<before> |
508 | calling this function, or cope with the fact afterwards (which is usually |
599 | calling this function, or cope with the fact afterwards (which is usually |
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
600 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
510 | for example). |
601 | for example). |
511 | |
602 | |
512 | Note that certain global state, such as signal state, will not be freed by |
603 | Note that certain global state, such as signal state (and installed signal |
513 | this function, and related watchers (such as signal and child watchers) |
604 | handlers), will not be freed by this function, and related watchers (such |
514 | would need to be stopped manually. |
605 | as signal and child watchers) would need to be stopped manually. |
515 | |
606 | |
516 | In general it is not advisable to call this function except in the |
607 | This function is normally used on loop objects allocated by |
517 | rare occasion where you really need to free e.g. the signal handling |
608 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
609 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
610 | |
|
|
611 | Note that it is not advisable to call this function on the default loop |
|
|
612 | except in the rare occasion where you really need to free it's resources. |
518 | pipe fds. If you need dynamically allocated loops it is better to use |
613 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
614 | and C<ev_loop_destroy>. |
520 | |
615 | |
521 | =item ev_loop_destroy (loop) |
616 | =item ev_loop_fork (loop) |
522 | |
617 | |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
524 | earlier call to C<ev_loop_new>. |
|
|
525 | |
|
|
526 | =item ev_default_fork () |
|
|
527 | |
|
|
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
618 | This function sets a flag that causes subsequent C<ev_run> iterations to |
529 | to reinitialise the kernel state for backends that have one. Despite the |
619 | reinitialise the kernel state for backends that have one. Despite the |
530 | name, you can call it anytime, but it makes most sense after forking, in |
620 | name, you can call it anytime, but it makes most sense after forking, in |
531 | the child process (or both child and parent, but that again makes little |
621 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
532 | sense). You I<must> call it in the child before using any of the libev |
622 | child before resuming or calling C<ev_run>. |
533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
623 | |
|
|
624 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
625 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
626 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
627 | during fork. |
534 | |
628 | |
535 | On the other hand, you only need to call this function in the child |
629 | On the other hand, you only need to call this function in the child |
536 | process if and only if you want to use the event library in the child. If |
630 | process if and only if you want to use the event loop in the child. If |
537 | you just fork+exec, you don't have to call it at all. |
631 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
632 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
633 | difference, but libev will usually detect this case on its own and do a |
|
|
634 | costly reset of the backend). |
538 | |
635 | |
539 | The function itself is quite fast and it's usually not a problem to call |
636 | The function itself is quite fast and it's usually not a problem to call |
540 | it just in case after a fork. To make this easy, the function will fit in |
637 | it just in case after a fork. |
541 | quite nicely into a call to C<pthread_atfork>: |
|
|
542 | |
638 | |
|
|
639 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
640 | using pthreads. |
|
|
641 | |
|
|
642 | static void |
|
|
643 | post_fork_child (void) |
|
|
644 | { |
|
|
645 | ev_loop_fork (EV_DEFAULT); |
|
|
646 | } |
|
|
647 | |
|
|
648 | ... |
543 | pthread_atfork (0, 0, ev_default_fork); |
649 | pthread_atfork (0, 0, post_fork_child); |
544 | |
|
|
545 | =item ev_loop_fork (loop) |
|
|
546 | |
|
|
547 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
549 | after fork, and how you do this is entirely your own problem. |
|
|
550 | |
650 | |
551 | =item int ev_is_default_loop (loop) |
651 | =item int ev_is_default_loop (loop) |
552 | |
652 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
653 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
654 | otherwise. |
554 | |
655 | |
555 | =item unsigned int ev_loop_count (loop) |
656 | =item unsigned int ev_iteration (loop) |
556 | |
657 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
658 | Returns the current iteration count for the event loop, which is identical |
558 | the number of times libev did poll for new events. It starts at C<0> and |
659 | to the number of times libev did poll for new events. It starts at C<0> |
559 | happily wraps around with enough iterations. |
660 | and happily wraps around with enough iterations. |
560 | |
661 | |
561 | This value can sometimes be useful as a generation counter of sorts (it |
662 | This value can sometimes be useful as a generation counter of sorts (it |
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
663 | "ticks" the number of loop iterations), as it roughly corresponds with |
563 | C<ev_prepare> and C<ev_check> calls. |
664 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
665 | prepare and check phases. |
|
|
666 | |
|
|
667 | =item unsigned int ev_depth (loop) |
|
|
668 | |
|
|
669 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
670 | times C<ev_run> was exited, in other words, the recursion depth. |
|
|
671 | |
|
|
672 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
673 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
674 | in which case it is higher. |
|
|
675 | |
|
|
676 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
|
|
677 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
678 | ungentleman-like behaviour unless it's really convenient. |
564 | |
679 | |
565 | =item unsigned int ev_backend (loop) |
680 | =item unsigned int ev_backend (loop) |
566 | |
681 | |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
682 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
568 | use. |
683 | use. |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
688 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
689 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
690 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
691 | event occurring (or more correctly, libev finding out about it). |
577 | |
692 | |
|
|
693 | =item ev_now_update (loop) |
|
|
694 | |
|
|
695 | Establishes the current time by querying the kernel, updating the time |
|
|
696 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
697 | is usually done automatically within C<ev_run ()>. |
|
|
698 | |
|
|
699 | This function is rarely useful, but when some event callback runs for a |
|
|
700 | very long time without entering the event loop, updating libev's idea of |
|
|
701 | the current time is a good idea. |
|
|
702 | |
|
|
703 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
704 | |
|
|
705 | =item ev_suspend (loop) |
|
|
706 | |
|
|
707 | =item ev_resume (loop) |
|
|
708 | |
|
|
709 | These two functions suspend and resume an event loop, for use when the |
|
|
710 | loop is not used for a while and timeouts should not be processed. |
|
|
711 | |
|
|
712 | A typical use case would be an interactive program such as a game: When |
|
|
713 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
714 | would be best to handle timeouts as if no time had actually passed while |
|
|
715 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
716 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
717 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
718 | |
|
|
719 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
720 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
721 | will be rescheduled (that is, they will lose any events that would have |
|
|
722 | occurred while suspended). |
|
|
723 | |
|
|
724 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
725 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
726 | without a previous call to C<ev_suspend>. |
|
|
727 | |
|
|
728 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
729 | event loop time (see C<ev_now_update>). |
|
|
730 | |
578 | =item ev_loop (loop, int flags) |
731 | =item ev_run (loop, int flags) |
579 | |
732 | |
580 | Finally, this is it, the event handler. This function usually is called |
733 | Finally, this is it, the event handler. This function usually is called |
581 | after you initialised all your watchers and you want to start handling |
734 | after you have initialised all your watchers and you want to start |
582 | events. |
735 | handling events. It will ask the operating system for any new events, call |
|
|
736 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
737 | is why event loops are called I<loops>. |
583 | |
738 | |
584 | If the flags argument is specified as C<0>, it will not return until |
739 | If the flags argument is specified as C<0>, it will keep handling events |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
740 | until either no event watchers are active anymore or C<ev_break> was |
|
|
741 | called. |
586 | |
742 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
743 | Please note that an explicit C<ev_break> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
744 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
745 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
746 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
747 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
748 | beauty. |
592 | |
749 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
750 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
751 | those events and any already outstanding ones, but will not wait and |
595 | case there are no events and will return after one iteration of the loop. |
752 | block your process in case there are no events and will return after one |
|
|
753 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
754 | events while doing lengthy calculations, to keep the program responsive. |
596 | |
755 | |
597 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
756 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
598 | necessary) and will handle those and any outstanding ones. It will block |
757 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
758 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
759 | be an event internal to libev itself, so there is no guarantee that a |
601 | external event in conjunction with something not expressible using other |
760 | user-registered callback will be called), and will return after one |
|
|
761 | iteration of the loop. |
|
|
762 | |
|
|
763 | This is useful if you are waiting for some external event in conjunction |
|
|
764 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
765 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
766 | usually a better approach for this kind of thing. |
604 | |
767 | |
605 | Here are the gory details of what C<ev_loop> does: |
768 | Here are the gory details of what C<ev_run> does: |
606 | |
769 | |
|
|
770 | - Increment loop depth. |
|
|
771 | - Reset the ev_break status. |
607 | - Before the first iteration, call any pending watchers. |
772 | - Before the first iteration, call any pending watchers. |
|
|
773 | LOOP: |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
774 | - If EVFLAG_FORKCHECK was used, check for a fork. |
609 | - If a fork was detected, queue and call all fork watchers. |
775 | - If a fork was detected (by any means), queue and call all fork watchers. |
610 | - Queue and call all prepare watchers. |
776 | - Queue and call all prepare watchers. |
|
|
777 | - If ev_break was called, goto FINISH. |
611 | - If we have been forked, recreate the kernel state. |
778 | - If we have been forked, detach and recreate the kernel state |
|
|
779 | as to not disturb the other process. |
612 | - Update the kernel state with all outstanding changes. |
780 | - Update the kernel state with all outstanding changes. |
613 | - Update the "event loop time". |
781 | - Update the "event loop time" (ev_now ()). |
614 | - Calculate for how long to sleep or block, if at all |
782 | - Calculate for how long to sleep or block, if at all |
615 | (active idle watchers, EVLOOP_NONBLOCK or not having |
783 | (active idle watchers, EVRUN_NOWAIT or not having |
616 | any active watchers at all will result in not sleeping). |
784 | any active watchers at all will result in not sleeping). |
617 | - Sleep if the I/O and timer collect interval say so. |
785 | - Sleep if the I/O and timer collect interval say so. |
|
|
786 | - Increment loop iteration counter. |
618 | - Block the process, waiting for any events. |
787 | - Block the process, waiting for any events. |
619 | - Queue all outstanding I/O (fd) events. |
788 | - Queue all outstanding I/O (fd) events. |
620 | - Update the "event loop time" and do time jump handling. |
789 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
621 | - Queue all outstanding timers. |
790 | - Queue all expired timers. |
622 | - Queue all outstanding periodics. |
791 | - Queue all expired periodics. |
623 | - If no events are pending now, queue all idle watchers. |
792 | - Queue all idle watchers with priority higher than that of pending events. |
624 | - Queue all check watchers. |
793 | - Queue all check watchers. |
625 | - Call all queued watchers in reverse order (i.e. check watchers first). |
794 | - Call all queued watchers in reverse order (i.e. check watchers first). |
626 | Signals and child watchers are implemented as I/O watchers, and will |
795 | Signals and child watchers are implemented as I/O watchers, and will |
627 | be handled here by queueing them when their watcher gets executed. |
796 | be handled here by queueing them when their watcher gets executed. |
628 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
797 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
629 | were used, or there are no active watchers, return, otherwise |
798 | were used, or there are no active watchers, goto FINISH, otherwise |
630 | continue with step *. |
799 | continue with step LOOP. |
|
|
800 | FINISH: |
|
|
801 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
802 | - Decrement the loop depth. |
|
|
803 | - Return. |
631 | |
804 | |
632 | Example: Queue some jobs and then loop until no events are outstanding |
805 | Example: Queue some jobs and then loop until no events are outstanding |
633 | anymore. |
806 | anymore. |
634 | |
807 | |
635 | ... queue jobs here, make sure they register event watchers as long |
808 | ... queue jobs here, make sure they register event watchers as long |
636 | ... as they still have work to do (even an idle watcher will do..) |
809 | ... as they still have work to do (even an idle watcher will do..) |
637 | ev_loop (my_loop, 0); |
810 | ev_run (my_loop, 0); |
638 | ... jobs done. yeah! |
811 | ... jobs done or somebody called unloop. yeah! |
639 | |
812 | |
640 | =item ev_unloop (loop, how) |
813 | =item ev_break (loop, how) |
641 | |
814 | |
642 | Can be used to make a call to C<ev_loop> return early (but only after it |
815 | Can be used to make a call to C<ev_run> return early (but only after it |
643 | has processed all outstanding events). The C<how> argument must be either |
816 | has processed all outstanding events). The C<how> argument must be either |
644 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
817 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
645 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
818 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
646 | |
819 | |
647 | This "unloop state" will be cleared when entering C<ev_loop> again. |
820 | This "unloop state" will be cleared when entering C<ev_run> again. |
|
|
821 | |
|
|
822 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
648 | |
823 | |
649 | =item ev_ref (loop) |
824 | =item ev_ref (loop) |
650 | |
825 | |
651 | =item ev_unref (loop) |
826 | =item ev_unref (loop) |
652 | |
827 | |
653 | Ref/unref can be used to add or remove a reference count on the event |
828 | Ref/unref can be used to add or remove a reference count on the event |
654 | loop: Every watcher keeps one reference, and as long as the reference |
829 | loop: Every watcher keeps one reference, and as long as the reference |
655 | count is nonzero, C<ev_loop> will not return on its own. If you have |
830 | count is nonzero, C<ev_run> will not return on its own. |
656 | a watcher you never unregister that should not keep C<ev_loop> from |
831 | |
657 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
832 | This is useful when you have a watcher that you never intend to |
|
|
833 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
834 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
835 | before stopping it. |
|
|
836 | |
658 | example, libev itself uses this for its internal signal pipe: It is not |
837 | As an example, libev itself uses this for its internal signal pipe: It |
659 | visible to the libev user and should not keep C<ev_loop> from exiting if |
838 | is not visible to the libev user and should not keep C<ev_run> from |
660 | no event watchers registered by it are active. It is also an excellent |
839 | exiting if no event watchers registered by it are active. It is also an |
661 | way to do this for generic recurring timers or from within third-party |
840 | excellent way to do this for generic recurring timers or from within |
662 | libraries. Just remember to I<unref after start> and I<ref before stop> |
841 | third-party libraries. Just remember to I<unref after start> and I<ref |
663 | (but only if the watcher wasn't active before, or was active before, |
842 | before stop> (but only if the watcher wasn't active before, or was active |
664 | respectively). |
843 | before, respectively. Note also that libev might stop watchers itself |
|
|
844 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
845 | in the callback). |
665 | |
846 | |
666 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
847 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
667 | running when nothing else is active. |
848 | running when nothing else is active. |
668 | |
849 | |
669 | struct ev_signal exitsig; |
850 | ev_signal exitsig; |
670 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
851 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
671 | ev_signal_start (loop, &exitsig); |
852 | ev_signal_start (loop, &exitsig); |
672 | evf_unref (loop); |
853 | evf_unref (loop); |
673 | |
854 | |
674 | Example: For some weird reason, unregister the above signal handler again. |
855 | Example: For some weird reason, unregister the above signal handler again. |
675 | |
856 | |
676 | ev_ref (loop); |
857 | ev_ref (loop); |
677 | ev_signal_stop (loop, &exitsig); |
858 | ev_signal_stop (loop, &exitsig); |
678 | |
859 | |
679 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
860 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
680 | |
861 | |
681 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
862 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
682 | |
863 | |
683 | These advanced functions influence the time that libev will spend waiting |
864 | These advanced functions influence the time that libev will spend waiting |
684 | for events. Both are by default C<0>, meaning that libev will try to |
865 | for events. Both time intervals are by default C<0>, meaning that libev |
685 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
866 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
867 | latency. |
686 | |
868 | |
687 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
869 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
688 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
870 | allows libev to delay invocation of I/O and timer/periodic callbacks |
689 | increase efficiency of loop iterations. |
871 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
872 | opportunities). |
690 | |
873 | |
691 | The background is that sometimes your program runs just fast enough to |
874 | The idea is that sometimes your program runs just fast enough to handle |
692 | handle one (or very few) event(s) per loop iteration. While this makes |
875 | one (or very few) event(s) per loop iteration. While this makes the |
693 | the program responsive, it also wastes a lot of CPU time to poll for new |
876 | program responsive, it also wastes a lot of CPU time to poll for new |
694 | events, especially with backends like C<select ()> which have a high |
877 | events, especially with backends like C<select ()> which have a high |
695 | overhead for the actual polling but can deliver many events at once. |
878 | overhead for the actual polling but can deliver many events at once. |
696 | |
879 | |
697 | By setting a higher I<io collect interval> you allow libev to spend more |
880 | By setting a higher I<io collect interval> you allow libev to spend more |
698 | time collecting I/O events, so you can handle more events per iteration, |
881 | time collecting I/O events, so you can handle more events per iteration, |
699 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
882 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
700 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
883 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
701 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
884 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
885 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
886 | once per this interval, on average. |
702 | |
887 | |
703 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
888 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
704 | to spend more time collecting timeouts, at the expense of increased |
889 | to spend more time collecting timeouts, at the expense of increased |
705 | latency (the watcher callback will be called later). C<ev_io> watchers |
890 | latency/jitter/inexactness (the watcher callback will be called |
706 | will not be affected. Setting this to a non-null value will not introduce |
891 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
707 | any overhead in libev. |
892 | value will not introduce any overhead in libev. |
708 | |
893 | |
709 | Many (busy) programs can usually benefit by setting the I/O collect |
894 | Many (busy) programs can usually benefit by setting the I/O collect |
710 | interval to a value near C<0.1> or so, which is often enough for |
895 | interval to a value near C<0.1> or so, which is often enough for |
711 | interactive servers (of course not for games), likewise for timeouts. It |
896 | interactive servers (of course not for games), likewise for timeouts. It |
712 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
897 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
713 | as this approaches the timing granularity of most systems. |
898 | as this approaches the timing granularity of most systems. Note that if |
|
|
899 | you do transactions with the outside world and you can't increase the |
|
|
900 | parallelity, then this setting will limit your transaction rate (if you |
|
|
901 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
902 | then you can't do more than 100 transactions per second). |
714 | |
903 | |
|
|
904 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
905 | saving power, as the program will "bundle" timer callback invocations that |
|
|
906 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
907 | times the process sleeps and wakes up again. Another useful technique to |
|
|
908 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
909 | they fire on, say, one-second boundaries only. |
|
|
910 | |
|
|
911 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
912 | more often than 100 times per second: |
|
|
913 | |
|
|
914 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
915 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
916 | |
|
|
917 | =item ev_invoke_pending (loop) |
|
|
918 | |
|
|
919 | This call will simply invoke all pending watchers while resetting their |
|
|
920 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
921 | but when overriding the invoke callback this call comes handy. This |
|
|
922 | function can be invoked from a watcher - this can be useful for example |
|
|
923 | when you want to do some lengthy calculation and want to pass further |
|
|
924 | event handling to another thread (you still have to make sure only one |
|
|
925 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
926 | |
|
|
927 | =item int ev_pending_count (loop) |
|
|
928 | |
|
|
929 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
930 | are pending. |
|
|
931 | |
|
|
932 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
933 | |
|
|
934 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
935 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
936 | this callback instead. This is useful, for example, when you want to |
|
|
937 | invoke the actual watchers inside another context (another thread etc.). |
|
|
938 | |
|
|
939 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
940 | callback. |
|
|
941 | |
|
|
942 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
943 | |
|
|
944 | Sometimes you want to share the same loop between multiple threads. This |
|
|
945 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
946 | each call to a libev function. |
|
|
947 | |
|
|
948 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
949 | to wait for it to return. One way around this is to wake up the event |
|
|
950 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
951 | I<release> and I<acquire> callbacks on the loop. |
|
|
952 | |
|
|
953 | When set, then C<release> will be called just before the thread is |
|
|
954 | suspended waiting for new events, and C<acquire> is called just |
|
|
955 | afterwards. |
|
|
956 | |
|
|
957 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
958 | C<acquire> will just call the mutex_lock function again. |
|
|
959 | |
|
|
960 | While event loop modifications are allowed between invocations of |
|
|
961 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
962 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
963 | have no effect on the set of file descriptors being watched, or the time |
|
|
964 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
965 | to take note of any changes you made. |
|
|
966 | |
|
|
967 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
968 | invocations of C<release> and C<acquire>. |
|
|
969 | |
|
|
970 | See also the locking example in the C<THREADS> section later in this |
|
|
971 | document. |
|
|
972 | |
|
|
973 | =item ev_set_userdata (loop, void *data) |
|
|
974 | |
|
|
975 | =item ev_userdata (loop) |
|
|
976 | |
|
|
977 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
978 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
979 | C<0.> |
|
|
980 | |
|
|
981 | These two functions can be used to associate arbitrary data with a loop, |
|
|
982 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
983 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
984 | any other purpose as well. |
|
|
985 | |
715 | =item ev_loop_verify (loop) |
986 | =item ev_verify (loop) |
716 | |
987 | |
717 | This function only does something when C<EV_VERIFY> support has been |
988 | This function only does something when C<EV_VERIFY> support has been |
718 | compiled in. It tries to go through all internal structures and checks |
989 | compiled in, which is the default for non-minimal builds. It tries to go |
719 | them for validity. If anything is found to be inconsistent, it will print |
990 | through all internal structures and checks them for validity. If anything |
720 | an error message to standard error and call C<abort ()>. |
991 | is found to be inconsistent, it will print an error message to standard |
|
|
992 | error and call C<abort ()>. |
721 | |
993 | |
722 | This can be used to catch bugs inside libev itself: under normal |
994 | This can be used to catch bugs inside libev itself: under normal |
723 | circumstances, this function will never abort as of course libev keeps its |
995 | circumstances, this function will never abort as of course libev keeps its |
724 | data structures consistent. |
996 | data structures consistent. |
725 | |
997 | |
726 | =back |
998 | =back |
727 | |
999 | |
728 | |
1000 | |
729 | =head1 ANATOMY OF A WATCHER |
1001 | =head1 ANATOMY OF A WATCHER |
730 | |
1002 | |
|
|
1003 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1004 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1005 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1006 | |
731 | A watcher is a structure that you create and register to record your |
1007 | A watcher is an opaque structure that you allocate and register to record |
732 | interest in some event. For instance, if you want to wait for STDIN to |
1008 | your interest in some event. To make a concrete example, imagine you want |
733 | become readable, you would create an C<ev_io> watcher for that: |
1009 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1010 | for that: |
734 | |
1011 | |
735 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1012 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
736 | { |
1013 | { |
737 | ev_io_stop (w); |
1014 | ev_io_stop (w); |
738 | ev_unloop (loop, EVUNLOOP_ALL); |
1015 | ev_break (loop, EVBREAK_ALL); |
739 | } |
1016 | } |
740 | |
1017 | |
741 | struct ev_loop *loop = ev_default_loop (0); |
1018 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1019 | |
742 | struct ev_io stdin_watcher; |
1020 | ev_io stdin_watcher; |
|
|
1021 | |
743 | ev_init (&stdin_watcher, my_cb); |
1022 | ev_init (&stdin_watcher, my_cb); |
744 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1023 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
745 | ev_io_start (loop, &stdin_watcher); |
1024 | ev_io_start (loop, &stdin_watcher); |
|
|
1025 | |
746 | ev_loop (loop, 0); |
1026 | ev_run (loop, 0); |
747 | |
1027 | |
748 | As you can see, you are responsible for allocating the memory for your |
1028 | As you can see, you are responsible for allocating the memory for your |
749 | watcher structures (and it is usually a bad idea to do this on the stack, |
1029 | watcher structures (and it is I<usually> a bad idea to do this on the |
750 | although this can sometimes be quite valid). |
1030 | stack). |
751 | |
1031 | |
|
|
1032 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1033 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1034 | |
752 | Each watcher structure must be initialised by a call to C<ev_init |
1035 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
753 | (watcher *, callback)>, which expects a callback to be provided. This |
1036 | *, callback)>, which expects a callback to be provided. This callback is |
754 | callback gets invoked each time the event occurs (or, in the case of I/O |
1037 | invoked each time the event occurs (or, in the case of I/O watchers, each |
755 | watchers, each time the event loop detects that the file descriptor given |
1038 | time the event loop detects that the file descriptor given is readable |
756 | is readable and/or writable). |
1039 | and/or writable). |
757 | |
1040 | |
758 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1041 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
759 | with arguments specific to this watcher type. There is also a macro |
1042 | macro to configure it, with arguments specific to the watcher type. There |
760 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1043 | is also a macro to combine initialisation and setting in one call: C<< |
761 | (watcher *, callback, ...) >>. |
1044 | ev_TYPE_init (watcher *, callback, ...) >>. |
762 | |
1045 | |
763 | To make the watcher actually watch out for events, you have to start it |
1046 | To make the watcher actually watch out for events, you have to start it |
764 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1047 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
765 | *) >>), and you can stop watching for events at any time by calling the |
1048 | *) >>), and you can stop watching for events at any time by calling the |
766 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1049 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
767 | |
1050 | |
768 | As long as your watcher is active (has been started but not stopped) you |
1051 | As long as your watcher is active (has been started but not stopped) you |
769 | must not touch the values stored in it. Most specifically you must never |
1052 | must not touch the values stored in it. Most specifically you must never |
770 | reinitialise it or call its C<set> macro. |
1053 | reinitialise it or call its C<ev_TYPE_set> macro. |
771 | |
1054 | |
772 | Each and every callback receives the event loop pointer as first, the |
1055 | Each and every callback receives the event loop pointer as first, the |
773 | registered watcher structure as second, and a bitset of received events as |
1056 | registered watcher structure as second, and a bitset of received events as |
774 | third argument. |
1057 | third argument. |
775 | |
1058 | |
… | |
… | |
784 | =item C<EV_WRITE> |
1067 | =item C<EV_WRITE> |
785 | |
1068 | |
786 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1069 | The file descriptor in the C<ev_io> watcher has become readable and/or |
787 | writable. |
1070 | writable. |
788 | |
1071 | |
789 | =item C<EV_TIMEOUT> |
1072 | =item C<EV_TIMER> |
790 | |
1073 | |
791 | The C<ev_timer> watcher has timed out. |
1074 | The C<ev_timer> watcher has timed out. |
792 | |
1075 | |
793 | =item C<EV_PERIODIC> |
1076 | =item C<EV_PERIODIC> |
794 | |
1077 | |
… | |
… | |
812 | |
1095 | |
813 | =item C<EV_PREPARE> |
1096 | =item C<EV_PREPARE> |
814 | |
1097 | |
815 | =item C<EV_CHECK> |
1098 | =item C<EV_CHECK> |
816 | |
1099 | |
817 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1100 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
818 | to gather new events, and all C<ev_check> watchers are invoked just after |
1101 | to gather new events, and all C<ev_check> watchers are invoked just after |
819 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1102 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
820 | received events. Callbacks of both watcher types can start and stop as |
1103 | received events. Callbacks of both watcher types can start and stop as |
821 | many watchers as they want, and all of them will be taken into account |
1104 | many watchers as they want, and all of them will be taken into account |
822 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1105 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
823 | C<ev_loop> from blocking). |
1106 | C<ev_run> from blocking). |
824 | |
1107 | |
825 | =item C<EV_EMBED> |
1108 | =item C<EV_EMBED> |
826 | |
1109 | |
827 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1110 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
828 | |
1111 | |
829 | =item C<EV_FORK> |
1112 | =item C<EV_FORK> |
830 | |
1113 | |
831 | The event loop has been resumed in the child process after fork (see |
1114 | The event loop has been resumed in the child process after fork (see |
832 | C<ev_fork>). |
1115 | C<ev_fork>). |
833 | |
1116 | |
|
|
1117 | =item C<EV_CLEANUP> |
|
|
1118 | |
|
|
1119 | The event loop is abotu to be destroyed (see C<ev_cleanup>). |
|
|
1120 | |
834 | =item C<EV_ASYNC> |
1121 | =item C<EV_ASYNC> |
835 | |
1122 | |
836 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1123 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1124 | |
|
|
1125 | =item C<EV_CUSTOM> |
|
|
1126 | |
|
|
1127 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1128 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
837 | |
1129 | |
838 | =item C<EV_ERROR> |
1130 | =item C<EV_ERROR> |
839 | |
1131 | |
840 | An unspecified error has occurred, the watcher has been stopped. This might |
1132 | An unspecified error has occurred, the watcher has been stopped. This might |
841 | happen because the watcher could not be properly started because libev |
1133 | happen because the watcher could not be properly started because libev |
842 | ran out of memory, a file descriptor was found to be closed or any other |
1134 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1135 | problem. Libev considers these application bugs. |
|
|
1136 | |
843 | problem. You best act on it by reporting the problem and somehow coping |
1137 | You best act on it by reporting the problem and somehow coping with the |
844 | with the watcher being stopped. |
1138 | watcher being stopped. Note that well-written programs should not receive |
|
|
1139 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1140 | bug in your program. |
845 | |
1141 | |
846 | Libev will usually signal a few "dummy" events together with an error, |
1142 | Libev will usually signal a few "dummy" events together with an error, for |
847 | for example it might indicate that a fd is readable or writable, and if |
1143 | example it might indicate that a fd is readable or writable, and if your |
848 | your callbacks is well-written it can just attempt the operation and cope |
1144 | callbacks is well-written it can just attempt the operation and cope with |
849 | with the error from read() or write(). This will not work in multi-threaded |
1145 | the error from read() or write(). This will not work in multi-threaded |
850 | programs, though, so beware. |
1146 | programs, though, as the fd could already be closed and reused for another |
|
|
1147 | thing, so beware. |
851 | |
1148 | |
852 | =back |
1149 | =back |
853 | |
1150 | |
|
|
1151 | =head2 WATCHER STATES |
|
|
1152 | |
|
|
1153 | There are various watcher states mentioned throughout this manual - |
|
|
1154 | active, pending and so on. In this section these states and the rules to |
|
|
1155 | transition between them will be described in more detail - and while these |
|
|
1156 | rules might look complicated, they usually do "the right thing". |
|
|
1157 | |
|
|
1158 | =over 4 |
|
|
1159 | |
|
|
1160 | =item initialiased |
|
|
1161 | |
|
|
1162 | Before a watcher can be registered with the event looop it has to be |
|
|
1163 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1164 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1165 | |
|
|
1166 | In this state it is simply some block of memory that is suitable for use |
|
|
1167 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1168 | |
|
|
1169 | =item started/running/active |
|
|
1170 | |
|
|
1171 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1172 | property of the event loop, and is actively waiting for events. While in |
|
|
1173 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1174 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1175 | and call libev functions on it that are documented to work on active watchers. |
|
|
1176 | |
|
|
1177 | =item pending |
|
|
1178 | |
|
|
1179 | If a watcher is active and libev determines that an event it is interested |
|
|
1180 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1181 | stay in this pending state until either it is stopped or its callback is |
|
|
1182 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1183 | callback. |
|
|
1184 | |
|
|
1185 | The watcher might or might not be active while it is pending (for example, |
|
|
1186 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1187 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1188 | but it is still property of the event loop at this time, so cannot be |
|
|
1189 | moved, freed or reused. And if it is active the rules described in the |
|
|
1190 | previous item still apply. |
|
|
1191 | |
|
|
1192 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1193 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1194 | active. |
|
|
1195 | |
|
|
1196 | =item stopped |
|
|
1197 | |
|
|
1198 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1199 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1200 | latter will clear any pending state the watcher might be in, regardless |
|
|
1201 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1202 | freeing it is often a good idea. |
|
|
1203 | |
|
|
1204 | While stopped (and not pending) the watcher is essentially in the |
|
|
1205 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1206 | you wish. |
|
|
1207 | |
|
|
1208 | =back |
|
|
1209 | |
854 | =head2 GENERIC WATCHER FUNCTIONS |
1210 | =head2 GENERIC WATCHER FUNCTIONS |
855 | |
|
|
856 | In the following description, C<TYPE> stands for the watcher type, |
|
|
857 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
858 | |
1211 | |
859 | =over 4 |
1212 | =over 4 |
860 | |
1213 | |
861 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1214 | =item C<ev_init> (ev_TYPE *watcher, callback) |
862 | |
1215 | |
… | |
… | |
868 | which rolls both calls into one. |
1221 | which rolls both calls into one. |
869 | |
1222 | |
870 | You can reinitialise a watcher at any time as long as it has been stopped |
1223 | You can reinitialise a watcher at any time as long as it has been stopped |
871 | (or never started) and there are no pending events outstanding. |
1224 | (or never started) and there are no pending events outstanding. |
872 | |
1225 | |
873 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1226 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
874 | int revents)>. |
1227 | int revents)>. |
875 | |
1228 | |
|
|
1229 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1230 | |
|
|
1231 | ev_io w; |
|
|
1232 | ev_init (&w, my_cb); |
|
|
1233 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1234 | |
876 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1235 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
877 | |
1236 | |
878 | This macro initialises the type-specific parts of a watcher. You need to |
1237 | This macro initialises the type-specific parts of a watcher. You need to |
879 | call C<ev_init> at least once before you call this macro, but you can |
1238 | call C<ev_init> at least once before you call this macro, but you can |
880 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1239 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
881 | macro on a watcher that is active (it can be pending, however, which is a |
1240 | macro on a watcher that is active (it can be pending, however, which is a |
882 | difference to the C<ev_init> macro). |
1241 | difference to the C<ev_init> macro). |
883 | |
1242 | |
884 | Although some watcher types do not have type-specific arguments |
1243 | Although some watcher types do not have type-specific arguments |
885 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1244 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
886 | |
1245 | |
|
|
1246 | See C<ev_init>, above, for an example. |
|
|
1247 | |
887 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1248 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
888 | |
1249 | |
889 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1250 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
890 | calls into a single call. This is the most convenient method to initialise |
1251 | calls into a single call. This is the most convenient method to initialise |
891 | a watcher. The same limitations apply, of course. |
1252 | a watcher. The same limitations apply, of course. |
892 | |
1253 | |
|
|
1254 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1255 | |
|
|
1256 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1257 | |
893 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1258 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
894 | |
1259 | |
895 | Starts (activates) the given watcher. Only active watchers will receive |
1260 | Starts (activates) the given watcher. Only active watchers will receive |
896 | events. If the watcher is already active nothing will happen. |
1261 | events. If the watcher is already active nothing will happen. |
897 | |
1262 | |
|
|
1263 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1264 | whole section. |
|
|
1265 | |
|
|
1266 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1267 | |
898 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1268 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
899 | |
1269 | |
900 | Stops the given watcher again (if active) and clears the pending |
1270 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1271 | the watcher was active or not). |
|
|
1272 | |
901 | status. It is possible that stopped watchers are pending (for example, |
1273 | It is possible that stopped watchers are pending - for example, |
902 | non-repeating timers are being stopped when they become pending), but |
1274 | non-repeating timers are being stopped when they become pending - but |
903 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1275 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
904 | you want to free or reuse the memory used by the watcher it is therefore a |
1276 | pending. If you want to free or reuse the memory used by the watcher it is |
905 | good idea to always call its C<ev_TYPE_stop> function. |
1277 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
906 | |
1278 | |
907 | =item bool ev_is_active (ev_TYPE *watcher) |
1279 | =item bool ev_is_active (ev_TYPE *watcher) |
908 | |
1280 | |
909 | Returns a true value iff the watcher is active (i.e. it has been started |
1281 | Returns a true value iff the watcher is active (i.e. it has been started |
910 | and not yet been stopped). As long as a watcher is active you must not modify |
1282 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
926 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1298 | =item ev_cb_set (ev_TYPE *watcher, callback) |
927 | |
1299 | |
928 | Change the callback. You can change the callback at virtually any time |
1300 | Change the callback. You can change the callback at virtually any time |
929 | (modulo threads). |
1301 | (modulo threads). |
930 | |
1302 | |
931 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1303 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
932 | |
1304 | |
933 | =item int ev_priority (ev_TYPE *watcher) |
1305 | =item int ev_priority (ev_TYPE *watcher) |
934 | |
1306 | |
935 | Set and query the priority of the watcher. The priority is a small |
1307 | Set and query the priority of the watcher. The priority is a small |
936 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1308 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
937 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1309 | (default: C<-2>). Pending watchers with higher priority will be invoked |
938 | before watchers with lower priority, but priority will not keep watchers |
1310 | before watchers with lower priority, but priority will not keep watchers |
939 | from being executed (except for C<ev_idle> watchers). |
1311 | from being executed (except for C<ev_idle> watchers). |
940 | |
1312 | |
941 | This means that priorities are I<only> used for ordering callback |
|
|
942 | invocation after new events have been received. This is useful, for |
|
|
943 | example, to reduce latency after idling, or more often, to bind two |
|
|
944 | watchers on the same event and make sure one is called first. |
|
|
945 | |
|
|
946 | If you need to suppress invocation when higher priority events are pending |
1313 | If you need to suppress invocation when higher priority events are pending |
947 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1314 | you need to look at C<ev_idle> watchers, which provide this functionality. |
948 | |
1315 | |
949 | You I<must not> change the priority of a watcher as long as it is active or |
1316 | You I<must not> change the priority of a watcher as long as it is active or |
950 | pending. |
1317 | pending. |
951 | |
1318 | |
|
|
1319 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1320 | fine, as long as you do not mind that the priority value you query might |
|
|
1321 | or might not have been clamped to the valid range. |
|
|
1322 | |
952 | The default priority used by watchers when no priority has been set is |
1323 | The default priority used by watchers when no priority has been set is |
953 | always C<0>, which is supposed to not be too high and not be too low :). |
1324 | always C<0>, which is supposed to not be too high and not be too low :). |
954 | |
1325 | |
955 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1326 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
956 | fine, as long as you do not mind that the priority value you query might |
1327 | priorities. |
957 | or might not have been adjusted to be within valid range. |
|
|
958 | |
1328 | |
959 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1329 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
960 | |
1330 | |
961 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1331 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
962 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1332 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
963 | can deal with that fact. |
1333 | can deal with that fact, as both are simply passed through to the |
|
|
1334 | callback. |
964 | |
1335 | |
965 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1336 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
966 | |
1337 | |
967 | If the watcher is pending, this function returns clears its pending status |
1338 | If the watcher is pending, this function clears its pending status and |
968 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1339 | returns its C<revents> bitset (as if its callback was invoked). If the |
969 | watcher isn't pending it does nothing and returns C<0>. |
1340 | watcher isn't pending it does nothing and returns C<0>. |
970 | |
1341 | |
|
|
1342 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1343 | callback to be invoked, which can be accomplished with this function. |
|
|
1344 | |
|
|
1345 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1346 | |
|
|
1347 | Feeds the given event set into the event loop, as if the specified event |
|
|
1348 | had happened for the specified watcher (which must be a pointer to an |
|
|
1349 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1350 | not free the watcher as long as it has pending events. |
|
|
1351 | |
|
|
1352 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1353 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1354 | not started in the first place. |
|
|
1355 | |
|
|
1356 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1357 | functions that do not need a watcher. |
|
|
1358 | |
971 | =back |
1359 | =back |
972 | |
1360 | |
973 | |
1361 | |
974 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
975 | |
1363 | |
976 | Each watcher has, by default, a member C<void *data> that you can change |
1364 | Each watcher has, by default, a member C<void *data> that you can change |
977 | and read at any time, libev will completely ignore it. This can be used |
1365 | and read at any time: libev will completely ignore it. This can be used |
978 | to associate arbitrary data with your watcher. If you need more data and |
1366 | to associate arbitrary data with your watcher. If you need more data and |
979 | don't want to allocate memory and store a pointer to it in that data |
1367 | don't want to allocate memory and store a pointer to it in that data |
980 | member, you can also "subclass" the watcher type and provide your own |
1368 | member, you can also "subclass" the watcher type and provide your own |
981 | data: |
1369 | data: |
982 | |
1370 | |
983 | struct my_io |
1371 | struct my_io |
984 | { |
1372 | { |
985 | struct ev_io io; |
1373 | ev_io io; |
986 | int otherfd; |
1374 | int otherfd; |
987 | void *somedata; |
1375 | void *somedata; |
988 | struct whatever *mostinteresting; |
1376 | struct whatever *mostinteresting; |
989 | } |
1377 | }; |
|
|
1378 | |
|
|
1379 | ... |
|
|
1380 | struct my_io w; |
|
|
1381 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
990 | |
1382 | |
991 | And since your callback will be called with a pointer to the watcher, you |
1383 | And since your callback will be called with a pointer to the watcher, you |
992 | can cast it back to your own type: |
1384 | can cast it back to your own type: |
993 | |
1385 | |
994 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1386 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
995 | { |
1387 | { |
996 | struct my_io *w = (struct my_io *)w_; |
1388 | struct my_io *w = (struct my_io *)w_; |
997 | ... |
1389 | ... |
998 | } |
1390 | } |
999 | |
1391 | |
1000 | More interesting and less C-conformant ways of casting your callback type |
1392 | More interesting and less C-conformant ways of casting your callback type |
1001 | instead have been omitted. |
1393 | instead have been omitted. |
1002 | |
1394 | |
1003 | Another common scenario is having some data structure with multiple |
1395 | Another common scenario is to use some data structure with multiple |
1004 | watchers: |
1396 | embedded watchers: |
1005 | |
1397 | |
1006 | struct my_biggy |
1398 | struct my_biggy |
1007 | { |
1399 | { |
1008 | int some_data; |
1400 | int some_data; |
1009 | ev_timer t1; |
1401 | ev_timer t1; |
1010 | ev_timer t2; |
1402 | ev_timer t2; |
1011 | } |
1403 | } |
1012 | |
1404 | |
1013 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1405 | In this case getting the pointer to C<my_biggy> is a bit more |
1014 | you need to use C<offsetof>: |
1406 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1407 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1408 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1409 | programmers): |
1015 | |
1410 | |
1016 | #include <stddef.h> |
1411 | #include <stddef.h> |
1017 | |
1412 | |
1018 | static void |
1413 | static void |
1019 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1414 | t1_cb (EV_P_ ev_timer *w, int revents) |
1020 | { |
1415 | { |
1021 | struct my_biggy big = (struct my_biggy * |
1416 | struct my_biggy big = (struct my_biggy *) |
1022 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1417 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1023 | } |
1418 | } |
1024 | |
1419 | |
1025 | static void |
1420 | static void |
1026 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1421 | t2_cb (EV_P_ ev_timer *w, int revents) |
1027 | { |
1422 | { |
1028 | struct my_biggy big = (struct my_biggy * |
1423 | struct my_biggy big = (struct my_biggy *) |
1029 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1424 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1030 | } |
1425 | } |
|
|
1426 | |
|
|
1427 | =head2 WATCHER PRIORITY MODELS |
|
|
1428 | |
|
|
1429 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1430 | integers that influence the ordering of event callback invocation |
|
|
1431 | between watchers in some way, all else being equal. |
|
|
1432 | |
|
|
1433 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1434 | description for the more technical details such as the actual priority |
|
|
1435 | range. |
|
|
1436 | |
|
|
1437 | There are two common ways how these these priorities are being interpreted |
|
|
1438 | by event loops: |
|
|
1439 | |
|
|
1440 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1441 | of lower priority watchers, which means as long as higher priority |
|
|
1442 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1443 | |
|
|
1444 | The less common only-for-ordering model uses priorities solely to order |
|
|
1445 | callback invocation within a single event loop iteration: Higher priority |
|
|
1446 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1447 | before polling for new events. |
|
|
1448 | |
|
|
1449 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1450 | except for idle watchers (which use the lock-out model). |
|
|
1451 | |
|
|
1452 | The rationale behind this is that implementing the lock-out model for |
|
|
1453 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1454 | libraries will just poll for the same events again and again as long as |
|
|
1455 | their callbacks have not been executed, which is very inefficient in the |
|
|
1456 | common case of one high-priority watcher locking out a mass of lower |
|
|
1457 | priority ones. |
|
|
1458 | |
|
|
1459 | Static (ordering) priorities are most useful when you have two or more |
|
|
1460 | watchers handling the same resource: a typical usage example is having an |
|
|
1461 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1462 | timeouts. Under load, data might be received while the program handles |
|
|
1463 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1464 | handler will be executed before checking for data. In that case, giving |
|
|
1465 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1466 | handled first even under adverse conditions (which is usually, but not |
|
|
1467 | always, what you want). |
|
|
1468 | |
|
|
1469 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1470 | will only be executed when no same or higher priority watchers have |
|
|
1471 | received events, they can be used to implement the "lock-out" model when |
|
|
1472 | required. |
|
|
1473 | |
|
|
1474 | For example, to emulate how many other event libraries handle priorities, |
|
|
1475 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1476 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1477 | processing is done in the idle watcher callback. This causes libev to |
|
|
1478 | continuously poll and process kernel event data for the watcher, but when |
|
|
1479 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1480 | workable. |
|
|
1481 | |
|
|
1482 | Usually, however, the lock-out model implemented that way will perform |
|
|
1483 | miserably under the type of load it was designed to handle. In that case, |
|
|
1484 | it might be preferable to stop the real watcher before starting the |
|
|
1485 | idle watcher, so the kernel will not have to process the event in case |
|
|
1486 | the actual processing will be delayed for considerable time. |
|
|
1487 | |
|
|
1488 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1489 | priority than the default, and which should only process data when no |
|
|
1490 | other events are pending: |
|
|
1491 | |
|
|
1492 | ev_idle idle; // actual processing watcher |
|
|
1493 | ev_io io; // actual event watcher |
|
|
1494 | |
|
|
1495 | static void |
|
|
1496 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1497 | { |
|
|
1498 | // stop the I/O watcher, we received the event, but |
|
|
1499 | // are not yet ready to handle it. |
|
|
1500 | ev_io_stop (EV_A_ w); |
|
|
1501 | |
|
|
1502 | // start the idle watcher to handle the actual event. |
|
|
1503 | // it will not be executed as long as other watchers |
|
|
1504 | // with the default priority are receiving events. |
|
|
1505 | ev_idle_start (EV_A_ &idle); |
|
|
1506 | } |
|
|
1507 | |
|
|
1508 | static void |
|
|
1509 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1510 | { |
|
|
1511 | // actual processing |
|
|
1512 | read (STDIN_FILENO, ...); |
|
|
1513 | |
|
|
1514 | // have to start the I/O watcher again, as |
|
|
1515 | // we have handled the event |
|
|
1516 | ev_io_start (EV_P_ &io); |
|
|
1517 | } |
|
|
1518 | |
|
|
1519 | // initialisation |
|
|
1520 | ev_idle_init (&idle, idle_cb); |
|
|
1521 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1522 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1523 | |
|
|
1524 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1525 | low-priority connections can not be locked out forever under load. This |
|
|
1526 | enables your program to keep a lower latency for important connections |
|
|
1527 | during short periods of high load, while not completely locking out less |
|
|
1528 | important ones. |
1031 | |
1529 | |
1032 | |
1530 | |
1033 | =head1 WATCHER TYPES |
1531 | =head1 WATCHER TYPES |
1034 | |
1532 | |
1035 | This section describes each watcher in detail, but will not repeat |
1533 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1059 | In general you can register as many read and/or write event watchers per |
1557 | In general you can register as many read and/or write event watchers per |
1060 | fd as you want (as long as you don't confuse yourself). Setting all file |
1558 | fd as you want (as long as you don't confuse yourself). Setting all file |
1061 | descriptors to non-blocking mode is also usually a good idea (but not |
1559 | descriptors to non-blocking mode is also usually a good idea (but not |
1062 | required if you know what you are doing). |
1560 | required if you know what you are doing). |
1063 | |
1561 | |
1064 | If you must do this, then force the use of a known-to-be-good backend |
1562 | If you cannot use non-blocking mode, then force the use of a |
1065 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1563 | known-to-be-good backend (at the time of this writing, this includes only |
1066 | C<EVBACKEND_POLL>). |
1564 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1565 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1566 | files) - libev doesn't guarantee any specific behaviour in that case. |
1067 | |
1567 | |
1068 | Another thing you have to watch out for is that it is quite easy to |
1568 | Another thing you have to watch out for is that it is quite easy to |
1069 | receive "spurious" readiness notifications, that is your callback might |
1569 | receive "spurious" readiness notifications, that is your callback might |
1070 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1570 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1071 | because there is no data. Not only are some backends known to create a |
1571 | because there is no data. Not only are some backends known to create a |
1072 | lot of those (for example Solaris ports), it is very easy to get into |
1572 | lot of those (for example Solaris ports), it is very easy to get into |
1073 | this situation even with a relatively standard program structure. Thus |
1573 | this situation even with a relatively standard program structure. Thus |
1074 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1574 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1075 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1575 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1076 | |
1576 | |
1077 | If you cannot run the fd in non-blocking mode (for example you should not |
1577 | If you cannot run the fd in non-blocking mode (for example you should |
1078 | play around with an Xlib connection), then you have to separately re-test |
1578 | not play around with an Xlib connection), then you have to separately |
1079 | whether a file descriptor is really ready with a known-to-be good interface |
1579 | re-test whether a file descriptor is really ready with a known-to-be good |
1080 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1580 | interface such as poll (fortunately in our Xlib example, Xlib already |
1081 | its own, so its quite safe to use). |
1581 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1582 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1583 | indefinitely. |
|
|
1584 | |
|
|
1585 | But really, best use non-blocking mode. |
1082 | |
1586 | |
1083 | =head3 The special problem of disappearing file descriptors |
1587 | =head3 The special problem of disappearing file descriptors |
1084 | |
1588 | |
1085 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1589 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1086 | descriptor (either by calling C<close> explicitly or by any other means, |
1590 | descriptor (either due to calling C<close> explicitly or any other means, |
1087 | such as C<dup>). The reason is that you register interest in some file |
1591 | such as C<dup2>). The reason is that you register interest in some file |
1088 | descriptor, but when it goes away, the operating system will silently drop |
1592 | descriptor, but when it goes away, the operating system will silently drop |
1089 | this interest. If another file descriptor with the same number then is |
1593 | this interest. If another file descriptor with the same number then is |
1090 | registered with libev, there is no efficient way to see that this is, in |
1594 | registered with libev, there is no efficient way to see that this is, in |
1091 | fact, a different file descriptor. |
1595 | fact, a different file descriptor. |
1092 | |
1596 | |
… | |
… | |
1123 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1627 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1124 | C<EVBACKEND_POLL>. |
1628 | C<EVBACKEND_POLL>. |
1125 | |
1629 | |
1126 | =head3 The special problem of SIGPIPE |
1630 | =head3 The special problem of SIGPIPE |
1127 | |
1631 | |
1128 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1632 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1129 | when reading from a pipe whose other end has been closed, your program |
1633 | when writing to a pipe whose other end has been closed, your program gets |
1130 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1634 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1131 | programs this is sensible behaviour, for daemons, this is usually |
1635 | this is sensible behaviour, for daemons, this is usually undesirable. |
1132 | undesirable. |
|
|
1133 | |
1636 | |
1134 | So when you encounter spurious, unexplained daemon exits, make sure you |
1637 | So when you encounter spurious, unexplained daemon exits, make sure you |
1135 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1638 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1136 | somewhere, as that would have given you a big clue). |
1639 | somewhere, as that would have given you a big clue). |
1137 | |
1640 | |
|
|
1641 | =head3 The special problem of accept()ing when you can't |
|
|
1642 | |
|
|
1643 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1644 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1645 | connection from the pending queue in all error cases. |
|
|
1646 | |
|
|
1647 | For example, larger servers often run out of file descriptors (because |
|
|
1648 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1649 | rejecting the connection, leading to libev signalling readiness on |
|
|
1650 | the next iteration again (the connection still exists after all), and |
|
|
1651 | typically causing the program to loop at 100% CPU usage. |
|
|
1652 | |
|
|
1653 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1654 | operating systems, there is usually little the app can do to remedy the |
|
|
1655 | situation, and no known thread-safe method of removing the connection to |
|
|
1656 | cope with overload is known (to me). |
|
|
1657 | |
|
|
1658 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1659 | - when the program encounters an overload, it will just loop until the |
|
|
1660 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1661 | event-based way to handle this situation, so it's the best one can do. |
|
|
1662 | |
|
|
1663 | A better way to handle the situation is to log any errors other than |
|
|
1664 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1665 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1666 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1667 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1668 | usage. |
|
|
1669 | |
|
|
1670 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1671 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1672 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1673 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1674 | clients under typical overload conditions. |
|
|
1675 | |
|
|
1676 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1677 | is often done with C<malloc> failures, but this results in an easy |
|
|
1678 | opportunity for a DoS attack. |
1138 | |
1679 | |
1139 | =head3 Watcher-Specific Functions |
1680 | =head3 Watcher-Specific Functions |
1140 | |
1681 | |
1141 | =over 4 |
1682 | =over 4 |
1142 | |
1683 | |
1143 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1684 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1144 | |
1685 | |
1145 | =item ev_io_set (ev_io *, int fd, int events) |
1686 | =item ev_io_set (ev_io *, int fd, int events) |
1146 | |
1687 | |
1147 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1688 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1148 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1689 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1149 | C<EV_READ | EV_WRITE> to receive the given events. |
1690 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1150 | |
1691 | |
1151 | =item int fd [read-only] |
1692 | =item int fd [read-only] |
1152 | |
1693 | |
1153 | The file descriptor being watched. |
1694 | The file descriptor being watched. |
1154 | |
1695 | |
… | |
… | |
1162 | |
1703 | |
1163 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1704 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1164 | readable, but only once. Since it is likely line-buffered, you could |
1705 | readable, but only once. Since it is likely line-buffered, you could |
1165 | attempt to read a whole line in the callback. |
1706 | attempt to read a whole line in the callback. |
1166 | |
1707 | |
1167 | static void |
1708 | static void |
1168 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1709 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1169 | { |
1710 | { |
1170 | ev_io_stop (loop, w); |
1711 | ev_io_stop (loop, w); |
1171 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1712 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1172 | } |
1713 | } |
1173 | |
1714 | |
1174 | ... |
1715 | ... |
1175 | struct ev_loop *loop = ev_default_init (0); |
1716 | struct ev_loop *loop = ev_default_init (0); |
1176 | struct ev_io stdin_readable; |
1717 | ev_io stdin_readable; |
1177 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1718 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1178 | ev_io_start (loop, &stdin_readable); |
1719 | ev_io_start (loop, &stdin_readable); |
1179 | ev_loop (loop, 0); |
1720 | ev_run (loop, 0); |
1180 | |
1721 | |
1181 | |
1722 | |
1182 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1723 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1183 | |
1724 | |
1184 | Timer watchers are simple relative timers that generate an event after a |
1725 | Timer watchers are simple relative timers that generate an event after a |
1185 | given time, and optionally repeating in regular intervals after that. |
1726 | given time, and optionally repeating in regular intervals after that. |
1186 | |
1727 | |
1187 | The timers are based on real time, that is, if you register an event that |
1728 | The timers are based on real time, that is, if you register an event that |
1188 | times out after an hour and you reset your system clock to January last |
1729 | times out after an hour and you reset your system clock to January last |
1189 | year, it will still time out after (roughly) and hour. "Roughly" because |
1730 | year, it will still time out after (roughly) one hour. "Roughly" because |
1190 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1731 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1191 | monotonic clock option helps a lot here). |
1732 | monotonic clock option helps a lot here). |
|
|
1733 | |
|
|
1734 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1735 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1736 | might introduce a small delay). If multiple timers become ready during the |
|
|
1737 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1738 | before ones of the same priority with later time-out values (but this is |
|
|
1739 | no longer true when a callback calls C<ev_run> recursively). |
|
|
1740 | |
|
|
1741 | =head3 Be smart about timeouts |
|
|
1742 | |
|
|
1743 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1744 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1745 | you want to raise some error after a while. |
|
|
1746 | |
|
|
1747 | What follows are some ways to handle this problem, from obvious and |
|
|
1748 | inefficient to smart and efficient. |
|
|
1749 | |
|
|
1750 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1751 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1752 | data or other life sign was received). |
|
|
1753 | |
|
|
1754 | =over 4 |
|
|
1755 | |
|
|
1756 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1757 | |
|
|
1758 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1759 | start the watcher: |
|
|
1760 | |
|
|
1761 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1762 | ev_timer_start (loop, timer); |
|
|
1763 | |
|
|
1764 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1765 | and start it again: |
|
|
1766 | |
|
|
1767 | ev_timer_stop (loop, timer); |
|
|
1768 | ev_timer_set (timer, 60., 0.); |
|
|
1769 | ev_timer_start (loop, timer); |
|
|
1770 | |
|
|
1771 | This is relatively simple to implement, but means that each time there is |
|
|
1772 | some activity, libev will first have to remove the timer from its internal |
|
|
1773 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1774 | still not a constant-time operation. |
|
|
1775 | |
|
|
1776 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1777 | |
|
|
1778 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1779 | C<ev_timer_start>. |
|
|
1780 | |
|
|
1781 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1782 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1783 | successfully read or write some data. If you go into an idle state where |
|
|
1784 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1785 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1786 | |
|
|
1787 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1788 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1789 | member and C<ev_timer_again>. |
|
|
1790 | |
|
|
1791 | At start: |
|
|
1792 | |
|
|
1793 | ev_init (timer, callback); |
|
|
1794 | timer->repeat = 60.; |
|
|
1795 | ev_timer_again (loop, timer); |
|
|
1796 | |
|
|
1797 | Each time there is some activity: |
|
|
1798 | |
|
|
1799 | ev_timer_again (loop, timer); |
|
|
1800 | |
|
|
1801 | It is even possible to change the time-out on the fly, regardless of |
|
|
1802 | whether the watcher is active or not: |
|
|
1803 | |
|
|
1804 | timer->repeat = 30.; |
|
|
1805 | ev_timer_again (loop, timer); |
|
|
1806 | |
|
|
1807 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1808 | you want to modify its timeout value, as libev does not have to completely |
|
|
1809 | remove and re-insert the timer from/into its internal data structure. |
|
|
1810 | |
|
|
1811 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1812 | |
|
|
1813 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1814 | |
|
|
1815 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1816 | relatively long compared to the intervals between other activity - in |
|
|
1817 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1818 | associated activity resets. |
|
|
1819 | |
|
|
1820 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1821 | but remember the time of last activity, and check for a real timeout only |
|
|
1822 | within the callback: |
|
|
1823 | |
|
|
1824 | ev_tstamp last_activity; // time of last activity |
|
|
1825 | |
|
|
1826 | static void |
|
|
1827 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1828 | { |
|
|
1829 | ev_tstamp now = ev_now (EV_A); |
|
|
1830 | ev_tstamp timeout = last_activity + 60.; |
|
|
1831 | |
|
|
1832 | // if last_activity + 60. is older than now, we did time out |
|
|
1833 | if (timeout < now) |
|
|
1834 | { |
|
|
1835 | // timeout occurred, take action |
|
|
1836 | } |
|
|
1837 | else |
|
|
1838 | { |
|
|
1839 | // callback was invoked, but there was some activity, re-arm |
|
|
1840 | // the watcher to fire in last_activity + 60, which is |
|
|
1841 | // guaranteed to be in the future, so "again" is positive: |
|
|
1842 | w->repeat = timeout - now; |
|
|
1843 | ev_timer_again (EV_A_ w); |
|
|
1844 | } |
|
|
1845 | } |
|
|
1846 | |
|
|
1847 | To summarise the callback: first calculate the real timeout (defined |
|
|
1848 | as "60 seconds after the last activity"), then check if that time has |
|
|
1849 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1850 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1851 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1852 | a timeout then. |
|
|
1853 | |
|
|
1854 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1855 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1856 | |
|
|
1857 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1858 | minus half the average time between activity), but virtually no calls to |
|
|
1859 | libev to change the timeout. |
|
|
1860 | |
|
|
1861 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1862 | to the current time (meaning we just have some activity :), then call the |
|
|
1863 | callback, which will "do the right thing" and start the timer: |
|
|
1864 | |
|
|
1865 | ev_init (timer, callback); |
|
|
1866 | last_activity = ev_now (loop); |
|
|
1867 | callback (loop, timer, EV_TIMER); |
|
|
1868 | |
|
|
1869 | And when there is some activity, simply store the current time in |
|
|
1870 | C<last_activity>, no libev calls at all: |
|
|
1871 | |
|
|
1872 | last_activity = ev_now (loop); |
|
|
1873 | |
|
|
1874 | This technique is slightly more complex, but in most cases where the |
|
|
1875 | time-out is unlikely to be triggered, much more efficient. |
|
|
1876 | |
|
|
1877 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1878 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1879 | fix things for you. |
|
|
1880 | |
|
|
1881 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1882 | |
|
|
1883 | If there is not one request, but many thousands (millions...), all |
|
|
1884 | employing some kind of timeout with the same timeout value, then one can |
|
|
1885 | do even better: |
|
|
1886 | |
|
|
1887 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1888 | at the I<end> of the list. |
|
|
1889 | |
|
|
1890 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1891 | the list is expected to fire (for example, using the technique #3). |
|
|
1892 | |
|
|
1893 | When there is some activity, remove the timer from the list, recalculate |
|
|
1894 | the timeout, append it to the end of the list again, and make sure to |
|
|
1895 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1896 | |
|
|
1897 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1898 | starting, stopping and updating the timers, at the expense of a major |
|
|
1899 | complication, and having to use a constant timeout. The constant timeout |
|
|
1900 | ensures that the list stays sorted. |
|
|
1901 | |
|
|
1902 | =back |
|
|
1903 | |
|
|
1904 | So which method the best? |
|
|
1905 | |
|
|
1906 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1907 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1908 | better, and isn't very complicated either. In most case, choosing either |
|
|
1909 | one is fine, with #3 being better in typical situations. |
|
|
1910 | |
|
|
1911 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1912 | rather complicated, but extremely efficient, something that really pays |
|
|
1913 | off after the first million or so of active timers, i.e. it's usually |
|
|
1914 | overkill :) |
|
|
1915 | |
|
|
1916 | =head3 The special problem of time updates |
|
|
1917 | |
|
|
1918 | Establishing the current time is a costly operation (it usually takes at |
|
|
1919 | least two system calls): EV therefore updates its idea of the current |
|
|
1920 | time only before and after C<ev_run> collects new events, which causes a |
|
|
1921 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1922 | lots of events in one iteration. |
1192 | |
1923 | |
1193 | The relative timeouts are calculated relative to the C<ev_now ()> |
1924 | The relative timeouts are calculated relative to the C<ev_now ()> |
1194 | time. This is usually the right thing as this timestamp refers to the time |
1925 | time. This is usually the right thing as this timestamp refers to the time |
1195 | of the event triggering whatever timeout you are modifying/starting. If |
1926 | of the event triggering whatever timeout you are modifying/starting. If |
1196 | you suspect event processing to be delayed and you I<need> to base the timeout |
1927 | you suspect event processing to be delayed and you I<need> to base the |
1197 | on the current time, use something like this to adjust for this: |
1928 | timeout on the current time, use something like this to adjust for this: |
1198 | |
1929 | |
1199 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1930 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1200 | |
1931 | |
1201 | The callback is guaranteed to be invoked only after its timeout has passed, |
1932 | If the event loop is suspended for a long time, you can also force an |
1202 | but if multiple timers become ready during the same loop iteration then |
1933 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1203 | order of execution is undefined. |
1934 | ()>. |
|
|
1935 | |
|
|
1936 | =head3 The special problems of suspended animation |
|
|
1937 | |
|
|
1938 | When you leave the server world it is quite customary to hit machines that |
|
|
1939 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1940 | |
|
|
1941 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1942 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1943 | to run until the system is suspended, but they will not advance while the |
|
|
1944 | system is suspended. That means, on resume, it will be as if the program |
|
|
1945 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1946 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1947 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1948 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1949 | be adjusted accordingly. |
|
|
1950 | |
|
|
1951 | I would not be surprised to see different behaviour in different between |
|
|
1952 | operating systems, OS versions or even different hardware. |
|
|
1953 | |
|
|
1954 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1955 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1956 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1957 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1958 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1959 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1960 | |
|
|
1961 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1962 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1963 | deterministic behaviour in this case (you can do nothing against |
|
|
1964 | C<SIGSTOP>). |
1204 | |
1965 | |
1205 | =head3 Watcher-Specific Functions and Data Members |
1966 | =head3 Watcher-Specific Functions and Data Members |
1206 | |
1967 | |
1207 | =over 4 |
1968 | =over 4 |
1208 | |
1969 | |
… | |
… | |
1232 | If the timer is started but non-repeating, stop it (as if it timed out). |
1993 | If the timer is started but non-repeating, stop it (as if it timed out). |
1233 | |
1994 | |
1234 | If the timer is repeating, either start it if necessary (with the |
1995 | If the timer is repeating, either start it if necessary (with the |
1235 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1996 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1236 | |
1997 | |
1237 | This sounds a bit complicated, but here is a useful and typical |
1998 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1238 | example: Imagine you have a TCP connection and you want a so-called idle |
1999 | usage example. |
1239 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1240 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1241 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1242 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1243 | you go into an idle state where you do not expect data to travel on the |
|
|
1244 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1245 | automatically restart it if need be. |
|
|
1246 | |
2000 | |
1247 | That means you can ignore the C<after> value and C<ev_timer_start> |
2001 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1248 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1249 | |
2002 | |
1250 | ev_timer_init (timer, callback, 0., 5.); |
2003 | Returns the remaining time until a timer fires. If the timer is active, |
1251 | ev_timer_again (loop, timer); |
2004 | then this time is relative to the current event loop time, otherwise it's |
1252 | ... |
2005 | the timeout value currently configured. |
1253 | timer->again = 17.; |
|
|
1254 | ev_timer_again (loop, timer); |
|
|
1255 | ... |
|
|
1256 | timer->again = 10.; |
|
|
1257 | ev_timer_again (loop, timer); |
|
|
1258 | |
2006 | |
1259 | This is more slightly efficient then stopping/starting the timer each time |
2007 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1260 | you want to modify its timeout value. |
2008 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2009 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2010 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2011 | too), and so on. |
1261 | |
2012 | |
1262 | =item ev_tstamp repeat [read-write] |
2013 | =item ev_tstamp repeat [read-write] |
1263 | |
2014 | |
1264 | The current C<repeat> value. Will be used each time the watcher times out |
2015 | The current C<repeat> value. Will be used each time the watcher times out |
1265 | or C<ev_timer_again> is called and determines the next timeout (if any), |
2016 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1266 | which is also when any modifications are taken into account. |
2017 | which is also when any modifications are taken into account. |
1267 | |
2018 | |
1268 | =back |
2019 | =back |
1269 | |
2020 | |
1270 | =head3 Examples |
2021 | =head3 Examples |
1271 | |
2022 | |
1272 | Example: Create a timer that fires after 60 seconds. |
2023 | Example: Create a timer that fires after 60 seconds. |
1273 | |
2024 | |
1274 | static void |
2025 | static void |
1275 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2026 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1276 | { |
2027 | { |
1277 | .. one minute over, w is actually stopped right here |
2028 | .. one minute over, w is actually stopped right here |
1278 | } |
2029 | } |
1279 | |
2030 | |
1280 | struct ev_timer mytimer; |
2031 | ev_timer mytimer; |
1281 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2032 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1282 | ev_timer_start (loop, &mytimer); |
2033 | ev_timer_start (loop, &mytimer); |
1283 | |
2034 | |
1284 | Example: Create a timeout timer that times out after 10 seconds of |
2035 | Example: Create a timeout timer that times out after 10 seconds of |
1285 | inactivity. |
2036 | inactivity. |
1286 | |
2037 | |
1287 | static void |
2038 | static void |
1288 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2039 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1289 | { |
2040 | { |
1290 | .. ten seconds without any activity |
2041 | .. ten seconds without any activity |
1291 | } |
2042 | } |
1292 | |
2043 | |
1293 | struct ev_timer mytimer; |
2044 | ev_timer mytimer; |
1294 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2045 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1295 | ev_timer_again (&mytimer); /* start timer */ |
2046 | ev_timer_again (&mytimer); /* start timer */ |
1296 | ev_loop (loop, 0); |
2047 | ev_run (loop, 0); |
1297 | |
2048 | |
1298 | // and in some piece of code that gets executed on any "activity": |
2049 | // and in some piece of code that gets executed on any "activity": |
1299 | // reset the timeout to start ticking again at 10 seconds |
2050 | // reset the timeout to start ticking again at 10 seconds |
1300 | ev_timer_again (&mytimer); |
2051 | ev_timer_again (&mytimer); |
1301 | |
2052 | |
1302 | |
2053 | |
1303 | =head2 C<ev_periodic> - to cron or not to cron? |
2054 | =head2 C<ev_periodic> - to cron or not to cron? |
1304 | |
2055 | |
1305 | Periodic watchers are also timers of a kind, but they are very versatile |
2056 | Periodic watchers are also timers of a kind, but they are very versatile |
1306 | (and unfortunately a bit complex). |
2057 | (and unfortunately a bit complex). |
1307 | |
2058 | |
1308 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2059 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1309 | but on wall clock time (absolute time). You can tell a periodic watcher |
2060 | relative time, the physical time that passes) but on wall clock time |
1310 | to trigger after some specific point in time. For example, if you tell a |
2061 | (absolute time, the thing you can read on your calender or clock). The |
1311 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2062 | difference is that wall clock time can run faster or slower than real |
1312 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2063 | time, and time jumps are not uncommon (e.g. when you adjust your |
1313 | clock to January of the previous year, then it will take more than year |
2064 | wrist-watch). |
1314 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1315 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1316 | |
2065 | |
|
|
2066 | You can tell a periodic watcher to trigger after some specific point |
|
|
2067 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2068 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2069 | not a delay) and then reset your system clock to January of the previous |
|
|
2070 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2071 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2072 | it, as it uses a relative timeout). |
|
|
2073 | |
1317 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2074 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1318 | such as triggering an event on each "midnight, local time", or other |
2075 | timers, such as triggering an event on each "midnight, local time", or |
1319 | complicated, rules. |
2076 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2077 | those cannot react to time jumps. |
1320 | |
2078 | |
1321 | As with timers, the callback is guaranteed to be invoked only when the |
2079 | As with timers, the callback is guaranteed to be invoked only when the |
1322 | time (C<at>) has passed, but if multiple periodic timers become ready |
2080 | point in time where it is supposed to trigger has passed. If multiple |
1323 | during the same loop iteration then order of execution is undefined. |
2081 | timers become ready during the same loop iteration then the ones with |
|
|
2082 | earlier time-out values are invoked before ones with later time-out values |
|
|
2083 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1324 | |
2084 | |
1325 | =head3 Watcher-Specific Functions and Data Members |
2085 | =head3 Watcher-Specific Functions and Data Members |
1326 | |
2086 | |
1327 | =over 4 |
2087 | =over 4 |
1328 | |
2088 | |
1329 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2089 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1330 | |
2090 | |
1331 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2091 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1332 | |
2092 | |
1333 | Lots of arguments, lets sort it out... There are basically three modes of |
2093 | Lots of arguments, let's sort it out... There are basically three modes of |
1334 | operation, and we will explain them from simplest to complex: |
2094 | operation, and we will explain them from simplest to most complex: |
1335 | |
2095 | |
1336 | =over 4 |
2096 | =over 4 |
1337 | |
2097 | |
1338 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2098 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1339 | |
2099 | |
1340 | In this configuration the watcher triggers an event after the wall clock |
2100 | In this configuration the watcher triggers an event after the wall clock |
1341 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2101 | time C<offset> has passed. It will not repeat and will not adjust when a |
1342 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2102 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1343 | run when the system time reaches or surpasses this time. |
2103 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2104 | this point in time. |
1344 | |
2105 | |
1345 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2106 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1346 | |
2107 | |
1347 | In this mode the watcher will always be scheduled to time out at the next |
2108 | In this mode the watcher will always be scheduled to time out at the next |
1348 | C<at + N * interval> time (for some integer N, which can also be negative) |
2109 | C<offset + N * interval> time (for some integer N, which can also be |
1349 | and then repeat, regardless of any time jumps. |
2110 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2111 | argument is merely an offset into the C<interval> periods. |
1350 | |
2112 | |
1351 | This can be used to create timers that do not drift with respect to system |
2113 | This can be used to create timers that do not drift with respect to the |
1352 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2114 | system clock, for example, here is an C<ev_periodic> that triggers each |
1353 | the hour: |
2115 | hour, on the hour (with respect to UTC): |
1354 | |
2116 | |
1355 | ev_periodic_set (&periodic, 0., 3600., 0); |
2117 | ev_periodic_set (&periodic, 0., 3600., 0); |
1356 | |
2118 | |
1357 | This doesn't mean there will always be 3600 seconds in between triggers, |
2119 | This doesn't mean there will always be 3600 seconds in between triggers, |
1358 | but only that the callback will be called when the system time shows a |
2120 | but only that the callback will be called when the system time shows a |
1359 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2121 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1360 | by 3600. |
2122 | by 3600. |
1361 | |
2123 | |
1362 | Another way to think about it (for the mathematically inclined) is that |
2124 | Another way to think about it (for the mathematically inclined) is that |
1363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2125 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1364 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2126 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1365 | |
2127 | |
1366 | For numerical stability it is preferable that the C<at> value is near |
2128 | For numerical stability it is preferable that the C<offset> value is near |
1367 | C<ev_now ()> (the current time), but there is no range requirement for |
2129 | C<ev_now ()> (the current time), but there is no range requirement for |
1368 | this value, and in fact is often specified as zero. |
2130 | this value, and in fact is often specified as zero. |
1369 | |
2131 | |
1370 | Note also that there is an upper limit to how often a timer can fire (CPU |
2132 | Note also that there is an upper limit to how often a timer can fire (CPU |
1371 | speed for example), so if C<interval> is very small then timing stability |
2133 | speed for example), so if C<interval> is very small then timing stability |
1372 | will of course deteriorate. Libev itself tries to be exact to be about one |
2134 | will of course deteriorate. Libev itself tries to be exact to be about one |
1373 | millisecond (if the OS supports it and the machine is fast enough). |
2135 | millisecond (if the OS supports it and the machine is fast enough). |
1374 | |
2136 | |
1375 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2137 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1376 | |
2138 | |
1377 | In this mode the values for C<interval> and C<at> are both being |
2139 | In this mode the values for C<interval> and C<offset> are both being |
1378 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2140 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1379 | reschedule callback will be called with the watcher as first, and the |
2141 | reschedule callback will be called with the watcher as first, and the |
1380 | current time as second argument. |
2142 | current time as second argument. |
1381 | |
2143 | |
1382 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2144 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1383 | ever, or make ANY event loop modifications whatsoever>. |
2145 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2146 | allowed by documentation here>. |
1384 | |
2147 | |
1385 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2148 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1386 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2149 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1387 | only event loop modification you are allowed to do). |
2150 | only event loop modification you are allowed to do). |
1388 | |
2151 | |
1389 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2152 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1390 | *w, ev_tstamp now)>, e.g.: |
2153 | *w, ev_tstamp now)>, e.g.: |
1391 | |
2154 | |
|
|
2155 | static ev_tstamp |
1392 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2156 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1393 | { |
2157 | { |
1394 | return now + 60.; |
2158 | return now + 60.; |
1395 | } |
2159 | } |
1396 | |
2160 | |
1397 | It must return the next time to trigger, based on the passed time value |
2161 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1417 | a different time than the last time it was called (e.g. in a crond like |
2181 | a different time than the last time it was called (e.g. in a crond like |
1418 | program when the crontabs have changed). |
2182 | program when the crontabs have changed). |
1419 | |
2183 | |
1420 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2184 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1421 | |
2185 | |
1422 | When active, returns the absolute time that the watcher is supposed to |
2186 | When active, returns the absolute time that the watcher is supposed |
1423 | trigger next. |
2187 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2188 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2189 | rescheduling modes. |
1424 | |
2190 | |
1425 | =item ev_tstamp offset [read-write] |
2191 | =item ev_tstamp offset [read-write] |
1426 | |
2192 | |
1427 | When repeating, this contains the offset value, otherwise this is the |
2193 | When repeating, this contains the offset value, otherwise this is the |
1428 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2194 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2195 | although libev might modify this value for better numerical stability). |
1429 | |
2196 | |
1430 | Can be modified any time, but changes only take effect when the periodic |
2197 | Can be modified any time, but changes only take effect when the periodic |
1431 | timer fires or C<ev_periodic_again> is being called. |
2198 | timer fires or C<ev_periodic_again> is being called. |
1432 | |
2199 | |
1433 | =item ev_tstamp interval [read-write] |
2200 | =item ev_tstamp interval [read-write] |
1434 | |
2201 | |
1435 | The current interval value. Can be modified any time, but changes only |
2202 | The current interval value. Can be modified any time, but changes only |
1436 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2203 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1437 | called. |
2204 | called. |
1438 | |
2205 | |
1439 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2206 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1440 | |
2207 | |
1441 | The current reschedule callback, or C<0>, if this functionality is |
2208 | The current reschedule callback, or C<0>, if this functionality is |
1442 | switched off. Can be changed any time, but changes only take effect when |
2209 | switched off. Can be changed any time, but changes only take effect when |
1443 | the periodic timer fires or C<ev_periodic_again> is being called. |
2210 | the periodic timer fires or C<ev_periodic_again> is being called. |
1444 | |
2211 | |
1445 | =back |
2212 | =back |
1446 | |
2213 | |
1447 | =head3 Examples |
2214 | =head3 Examples |
1448 | |
2215 | |
1449 | Example: Call a callback every hour, or, more precisely, whenever the |
2216 | Example: Call a callback every hour, or, more precisely, whenever the |
1450 | system clock is divisible by 3600. The callback invocation times have |
2217 | system time is divisible by 3600. The callback invocation times have |
1451 | potentially a lot of jitter, but good long-term stability. |
2218 | potentially a lot of jitter, but good long-term stability. |
1452 | |
2219 | |
1453 | static void |
2220 | static void |
1454 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2221 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1455 | { |
2222 | { |
1456 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2223 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1457 | } |
2224 | } |
1458 | |
2225 | |
1459 | struct ev_periodic hourly_tick; |
2226 | ev_periodic hourly_tick; |
1460 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2227 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1461 | ev_periodic_start (loop, &hourly_tick); |
2228 | ev_periodic_start (loop, &hourly_tick); |
1462 | |
2229 | |
1463 | Example: The same as above, but use a reschedule callback to do it: |
2230 | Example: The same as above, but use a reschedule callback to do it: |
1464 | |
2231 | |
1465 | #include <math.h> |
2232 | #include <math.h> |
1466 | |
2233 | |
1467 | static ev_tstamp |
2234 | static ev_tstamp |
1468 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2235 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1469 | { |
2236 | { |
1470 | return fmod (now, 3600.) + 3600.; |
2237 | return now + (3600. - fmod (now, 3600.)); |
1471 | } |
2238 | } |
1472 | |
2239 | |
1473 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2240 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1474 | |
2241 | |
1475 | Example: Call a callback every hour, starting now: |
2242 | Example: Call a callback every hour, starting now: |
1476 | |
2243 | |
1477 | struct ev_periodic hourly_tick; |
2244 | ev_periodic hourly_tick; |
1478 | ev_periodic_init (&hourly_tick, clock_cb, |
2245 | ev_periodic_init (&hourly_tick, clock_cb, |
1479 | fmod (ev_now (loop), 3600.), 3600., 0); |
2246 | fmod (ev_now (loop), 3600.), 3600., 0); |
1480 | ev_periodic_start (loop, &hourly_tick); |
2247 | ev_periodic_start (loop, &hourly_tick); |
1481 | |
2248 | |
1482 | |
2249 | |
1483 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2250 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1484 | |
2251 | |
1485 | Signal watchers will trigger an event when the process receives a specific |
2252 | Signal watchers will trigger an event when the process receives a specific |
1486 | signal one or more times. Even though signals are very asynchronous, libev |
2253 | signal one or more times. Even though signals are very asynchronous, libev |
1487 | will try it's best to deliver signals synchronously, i.e. as part of the |
2254 | will try it's best to deliver signals synchronously, i.e. as part of the |
1488 | normal event processing, like any other event. |
2255 | normal event processing, like any other event. |
1489 | |
2256 | |
|
|
2257 | If you want signals to be delivered truly asynchronously, just use |
|
|
2258 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2259 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2260 | synchronously wake up an event loop. |
|
|
2261 | |
1490 | You can configure as many watchers as you like per signal. Only when the |
2262 | You can configure as many watchers as you like for the same signal, but |
|
|
2263 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2264 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2265 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2266 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2267 | |
1491 | first watcher gets started will libev actually register a signal watcher |
2268 | When the first watcher gets started will libev actually register something |
1492 | with the kernel (thus it coexists with your own signal handlers as long |
2269 | with the kernel (thus it coexists with your own signal handlers as long as |
1493 | as you don't register any with libev). Similarly, when the last signal |
2270 | you don't register any with libev for the same signal). |
1494 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1495 | SIG_DFL (regardless of what it was set to before). |
|
|
1496 | |
2271 | |
1497 | If possible and supported, libev will install its handlers with |
2272 | If possible and supported, libev will install its handlers with |
1498 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2273 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1499 | interrupted. If you have a problem with system calls getting interrupted by |
2274 | not be unduly interrupted. If you have a problem with system calls getting |
1500 | signals you can block all signals in an C<ev_check> watcher and unblock |
2275 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1501 | them in an C<ev_prepare> watcher. |
2276 | and unblock them in an C<ev_prepare> watcher. |
|
|
2277 | |
|
|
2278 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2279 | |
|
|
2280 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2281 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2282 | stopping it again), that is, libev might or might not block the signal, |
|
|
2283 | and might or might not set or restore the installed signal handler. |
|
|
2284 | |
|
|
2285 | While this does not matter for the signal disposition (libev never |
|
|
2286 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2287 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2288 | certain signals to be blocked. |
|
|
2289 | |
|
|
2290 | This means that before calling C<exec> (from the child) you should reset |
|
|
2291 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2292 | choice usually). |
|
|
2293 | |
|
|
2294 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2295 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2296 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2297 | |
|
|
2298 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2299 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2300 | the window of opportunity for problems, it will not go away, as libev |
|
|
2301 | I<has> to modify the signal mask, at least temporarily. |
|
|
2302 | |
|
|
2303 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2304 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2305 | is not a libev-specific thing, this is true for most event libraries. |
1502 | |
2306 | |
1503 | =head3 Watcher-Specific Functions and Data Members |
2307 | =head3 Watcher-Specific Functions and Data Members |
1504 | |
2308 | |
1505 | =over 4 |
2309 | =over 4 |
1506 | |
2310 | |
… | |
… | |
1517 | |
2321 | |
1518 | =back |
2322 | =back |
1519 | |
2323 | |
1520 | =head3 Examples |
2324 | =head3 Examples |
1521 | |
2325 | |
1522 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2326 | Example: Try to exit cleanly on SIGINT. |
1523 | |
2327 | |
1524 | static void |
2328 | static void |
1525 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2329 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1526 | { |
2330 | { |
1527 | ev_unloop (loop, EVUNLOOP_ALL); |
2331 | ev_break (loop, EVBREAK_ALL); |
1528 | } |
2332 | } |
1529 | |
2333 | |
1530 | struct ev_signal signal_watcher; |
2334 | ev_signal signal_watcher; |
1531 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2335 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1532 | ev_signal_start (loop, &sigint_cb); |
2336 | ev_signal_start (loop, &signal_watcher); |
1533 | |
2337 | |
1534 | |
2338 | |
1535 | =head2 C<ev_child> - watch out for process status changes |
2339 | =head2 C<ev_child> - watch out for process status changes |
1536 | |
2340 | |
1537 | Child watchers trigger when your process receives a SIGCHLD in response to |
2341 | Child watchers trigger when your process receives a SIGCHLD in response to |
1538 | some child status changes (most typically when a child of yours dies). It |
2342 | some child status changes (most typically when a child of yours dies or |
1539 | is permissible to install a child watcher I<after> the child has been |
2343 | exits). It is permissible to install a child watcher I<after> the child |
1540 | forked (which implies it might have already exited), as long as the event |
2344 | has been forked (which implies it might have already exited), as long |
1541 | loop isn't entered (or is continued from a watcher). |
2345 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2346 | forking and then immediately registering a watcher for the child is fine, |
|
|
2347 | but forking and registering a watcher a few event loop iterations later or |
|
|
2348 | in the next callback invocation is not. |
1542 | |
2349 | |
1543 | Only the default event loop is capable of handling signals, and therefore |
2350 | Only the default event loop is capable of handling signals, and therefore |
1544 | you can only register child watchers in the default event loop. |
2351 | you can only register child watchers in the default event loop. |
1545 | |
2352 | |
|
|
2353 | Due to some design glitches inside libev, child watchers will always be |
|
|
2354 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2355 | libev) |
|
|
2356 | |
1546 | =head3 Process Interaction |
2357 | =head3 Process Interaction |
1547 | |
2358 | |
1548 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2359 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1549 | initialised. This is necessary to guarantee proper behaviour even if |
2360 | initialised. This is necessary to guarantee proper behaviour even if the |
1550 | the first child watcher is started after the child exits. The occurrence |
2361 | first child watcher is started after the child exits. The occurrence |
1551 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2362 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1552 | synchronously as part of the event loop processing. Libev always reaps all |
2363 | synchronously as part of the event loop processing. Libev always reaps all |
1553 | children, even ones not watched. |
2364 | children, even ones not watched. |
1554 | |
2365 | |
1555 | =head3 Overriding the Built-In Processing |
2366 | =head3 Overriding the Built-In Processing |
… | |
… | |
1559 | handler, you can override it easily by installing your own handler for |
2370 | handler, you can override it easily by installing your own handler for |
1560 | C<SIGCHLD> after initialising the default loop, and making sure the |
2371 | C<SIGCHLD> after initialising the default loop, and making sure the |
1561 | default loop never gets destroyed. You are encouraged, however, to use an |
2372 | default loop never gets destroyed. You are encouraged, however, to use an |
1562 | event-based approach to child reaping and thus use libev's support for |
2373 | event-based approach to child reaping and thus use libev's support for |
1563 | that, so other libev users can use C<ev_child> watchers freely. |
2374 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2375 | |
|
|
2376 | =head3 Stopping the Child Watcher |
|
|
2377 | |
|
|
2378 | Currently, the child watcher never gets stopped, even when the |
|
|
2379 | child terminates, so normally one needs to stop the watcher in the |
|
|
2380 | callback. Future versions of libev might stop the watcher automatically |
|
|
2381 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2382 | problem). |
1564 | |
2383 | |
1565 | =head3 Watcher-Specific Functions and Data Members |
2384 | =head3 Watcher-Specific Functions and Data Members |
1566 | |
2385 | |
1567 | =over 4 |
2386 | =over 4 |
1568 | |
2387 | |
… | |
… | |
1597 | =head3 Examples |
2416 | =head3 Examples |
1598 | |
2417 | |
1599 | Example: C<fork()> a new process and install a child handler to wait for |
2418 | Example: C<fork()> a new process and install a child handler to wait for |
1600 | its completion. |
2419 | its completion. |
1601 | |
2420 | |
1602 | ev_child cw; |
2421 | ev_child cw; |
1603 | |
2422 | |
1604 | static void |
2423 | static void |
1605 | child_cb (EV_P_ struct ev_child *w, int revents) |
2424 | child_cb (EV_P_ ev_child *w, int revents) |
1606 | { |
2425 | { |
1607 | ev_child_stop (EV_A_ w); |
2426 | ev_child_stop (EV_A_ w); |
1608 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2427 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1609 | } |
2428 | } |
1610 | |
2429 | |
1611 | pid_t pid = fork (); |
2430 | pid_t pid = fork (); |
1612 | |
2431 | |
1613 | if (pid < 0) |
2432 | if (pid < 0) |
1614 | // error |
2433 | // error |
1615 | else if (pid == 0) |
2434 | else if (pid == 0) |
1616 | { |
2435 | { |
1617 | // the forked child executes here |
2436 | // the forked child executes here |
1618 | exit (1); |
2437 | exit (1); |
1619 | } |
2438 | } |
1620 | else |
2439 | else |
1621 | { |
2440 | { |
1622 | ev_child_init (&cw, child_cb, pid, 0); |
2441 | ev_child_init (&cw, child_cb, pid, 0); |
1623 | ev_child_start (EV_DEFAULT_ &cw); |
2442 | ev_child_start (EV_DEFAULT_ &cw); |
1624 | } |
2443 | } |
1625 | |
2444 | |
1626 | |
2445 | |
1627 | =head2 C<ev_stat> - did the file attributes just change? |
2446 | =head2 C<ev_stat> - did the file attributes just change? |
1628 | |
2447 | |
1629 | This watches a file system path for attribute changes. That is, it calls |
2448 | This watches a file system path for attribute changes. That is, it calls |
1630 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2449 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1631 | compared to the last time, invoking the callback if it did. |
2450 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2451 | it did. |
1632 | |
2452 | |
1633 | The path does not need to exist: changing from "path exists" to "path does |
2453 | The path does not need to exist: changing from "path exists" to "path does |
1634 | not exist" is a status change like any other. The condition "path does |
2454 | not exist" is a status change like any other. The condition "path does not |
1635 | not exist" is signified by the C<st_nlink> field being zero (which is |
2455 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1636 | otherwise always forced to be at least one) and all the other fields of |
2456 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1637 | the stat buffer having unspecified contents. |
2457 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2458 | contents. |
1638 | |
2459 | |
1639 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2460 | The path I<must not> end in a slash or contain special components such as |
|
|
2461 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1640 | relative and your working directory changes, the behaviour is undefined. |
2462 | your working directory changes, then the behaviour is undefined. |
1641 | |
2463 | |
1642 | Since there is no standard to do this, the portable implementation simply |
2464 | Since there is no portable change notification interface available, the |
1643 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2465 | portable implementation simply calls C<stat(2)> regularly on the path |
1644 | can specify a recommended polling interval for this case. If you specify |
2466 | to see if it changed somehow. You can specify a recommended polling |
1645 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2467 | interval for this case. If you specify a polling interval of C<0> (highly |
1646 | unspecified default> value will be used (which you can expect to be around |
2468 | recommended!) then a I<suitable, unspecified default> value will be used |
1647 | five seconds, although this might change dynamically). Libev will also |
2469 | (which you can expect to be around five seconds, although this might |
1648 | impose a minimum interval which is currently around C<0.1>, but thats |
2470 | change dynamically). Libev will also impose a minimum interval which is |
1649 | usually overkill. |
2471 | currently around C<0.1>, but that's usually overkill. |
1650 | |
2472 | |
1651 | This watcher type is not meant for massive numbers of stat watchers, |
2473 | This watcher type is not meant for massive numbers of stat watchers, |
1652 | as even with OS-supported change notifications, this can be |
2474 | as even with OS-supported change notifications, this can be |
1653 | resource-intensive. |
2475 | resource-intensive. |
1654 | |
2476 | |
1655 | At the time of this writing, only the Linux inotify interface is |
2477 | At the time of this writing, the only OS-specific interface implemented |
1656 | implemented (implementing kqueue support is left as an exercise for the |
2478 | is the Linux inotify interface (implementing kqueue support is left as an |
1657 | reader, note, however, that the author sees no way of implementing ev_stat |
2479 | exercise for the reader. Note, however, that the author sees no way of |
1658 | semantics with kqueue). Inotify will be used to give hints only and should |
2480 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1659 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1660 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1661 | but changes are usually detected immediately, and if the file exists there |
|
|
1662 | will be no polling. |
|
|
1663 | |
2481 | |
1664 | =head3 ABI Issues (Largefile Support) |
2482 | =head3 ABI Issues (Largefile Support) |
1665 | |
2483 | |
1666 | Libev by default (unless the user overrides this) uses the default |
2484 | Libev by default (unless the user overrides this) uses the default |
1667 | compilation environment, which means that on systems with optionally |
2485 | compilation environment, which means that on systems with large file |
1668 | disabled large file support, you get the 32 bit version of the stat |
2486 | support disabled by default, you get the 32 bit version of the stat |
1669 | structure. When using the library from programs that change the ABI to |
2487 | structure. When using the library from programs that change the ABI to |
1670 | use 64 bit file offsets the programs will fail. In that case you have to |
2488 | use 64 bit file offsets the programs will fail. In that case you have to |
1671 | compile libev with the same flags to get binary compatibility. This is |
2489 | compile libev with the same flags to get binary compatibility. This is |
1672 | obviously the case with any flags that change the ABI, but the problem is |
2490 | obviously the case with any flags that change the ABI, but the problem is |
1673 | most noticeably with ev_stat and large file support. |
2491 | most noticeably displayed with ev_stat and large file support. |
1674 | |
2492 | |
1675 | =head3 Inotify |
2493 | The solution for this is to lobby your distribution maker to make large |
|
|
2494 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2495 | optional. Libev cannot simply switch on large file support because it has |
|
|
2496 | to exchange stat structures with application programs compiled using the |
|
|
2497 | default compilation environment. |
1676 | |
2498 | |
|
|
2499 | =head3 Inotify and Kqueue |
|
|
2500 | |
1677 | When C<inotify (7)> support has been compiled into libev (generally only |
2501 | When C<inotify (7)> support has been compiled into libev and present at |
1678 | available on Linux) and present at runtime, it will be used to speed up |
2502 | runtime, it will be used to speed up change detection where possible. The |
1679 | change detection where possible. The inotify descriptor will be created lazily |
2503 | inotify descriptor will be created lazily when the first C<ev_stat> |
1680 | when the first C<ev_stat> watcher is being started. |
2504 | watcher is being started. |
1681 | |
2505 | |
1682 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2506 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1683 | except that changes might be detected earlier, and in some cases, to avoid |
2507 | except that changes might be detected earlier, and in some cases, to avoid |
1684 | making regular C<stat> calls. Even in the presence of inotify support |
2508 | making regular C<stat> calls. Even in the presence of inotify support |
1685 | there are many cases where libev has to resort to regular C<stat> polling. |
2509 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2510 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2511 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2512 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2513 | xfs are fully working) libev usually gets away without polling. |
1686 | |
2514 | |
1687 | (There is no support for kqueue, as apparently it cannot be used to |
2515 | There is no support for kqueue, as apparently it cannot be used to |
1688 | implement this functionality, due to the requirement of having a file |
2516 | implement this functionality, due to the requirement of having a file |
1689 | descriptor open on the object at all times). |
2517 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2518 | etc. is difficult. |
|
|
2519 | |
|
|
2520 | =head3 C<stat ()> is a synchronous operation |
|
|
2521 | |
|
|
2522 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2523 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2524 | ()>, which is a synchronous operation. |
|
|
2525 | |
|
|
2526 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2527 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2528 | as the path data is usually in memory already (except when starting the |
|
|
2529 | watcher). |
|
|
2530 | |
|
|
2531 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2532 | time due to network issues, and even under good conditions, a stat call |
|
|
2533 | often takes multiple milliseconds. |
|
|
2534 | |
|
|
2535 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2536 | paths, although this is fully supported by libev. |
1690 | |
2537 | |
1691 | =head3 The special problem of stat time resolution |
2538 | =head3 The special problem of stat time resolution |
1692 | |
2539 | |
1693 | The C<stat ()> system call only supports full-second resolution portably, and |
2540 | The C<stat ()> system call only supports full-second resolution portably, |
1694 | even on systems where the resolution is higher, many file systems still |
2541 | and even on systems where the resolution is higher, most file systems |
1695 | only support whole seconds. |
2542 | still only support whole seconds. |
1696 | |
2543 | |
1697 | That means that, if the time is the only thing that changes, you can |
2544 | That means that, if the time is the only thing that changes, you can |
1698 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2545 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1699 | calls your callback, which does something. When there is another update |
2546 | calls your callback, which does something. When there is another update |
1700 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2547 | within the same second, C<ev_stat> will be unable to detect unless the |
1701 | data does not change. |
2548 | stat data does change in other ways (e.g. file size). |
1702 | |
2549 | |
1703 | The solution to this is to delay acting on a change for slightly more |
2550 | The solution to this is to delay acting on a change for slightly more |
1704 | than a second (or till slightly after the next full second boundary), using |
2551 | than a second (or till slightly after the next full second boundary), using |
1705 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2552 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1706 | ev_timer_again (loop, w)>). |
2553 | ev_timer_again (loop, w)>). |
… | |
… | |
1726 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2573 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1727 | be detected and should normally be specified as C<0> to let libev choose |
2574 | be detected and should normally be specified as C<0> to let libev choose |
1728 | a suitable value. The memory pointed to by C<path> must point to the same |
2575 | a suitable value. The memory pointed to by C<path> must point to the same |
1729 | path for as long as the watcher is active. |
2576 | path for as long as the watcher is active. |
1730 | |
2577 | |
1731 | The callback will receive C<EV_STAT> when a change was detected, relative |
2578 | The callback will receive an C<EV_STAT> event when a change was detected, |
1732 | to the attributes at the time the watcher was started (or the last change |
2579 | relative to the attributes at the time the watcher was started (or the |
1733 | was detected). |
2580 | last change was detected). |
1734 | |
2581 | |
1735 | =item ev_stat_stat (loop, ev_stat *) |
2582 | =item ev_stat_stat (loop, ev_stat *) |
1736 | |
2583 | |
1737 | Updates the stat buffer immediately with new values. If you change the |
2584 | Updates the stat buffer immediately with new values. If you change the |
1738 | watched path in your callback, you could call this function to avoid |
2585 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1767 | |
2614 | |
1768 | =head3 Examples |
2615 | =head3 Examples |
1769 | |
2616 | |
1770 | Example: Watch C</etc/passwd> for attribute changes. |
2617 | Example: Watch C</etc/passwd> for attribute changes. |
1771 | |
2618 | |
1772 | static void |
2619 | static void |
1773 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2620 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1774 | { |
2621 | { |
1775 | /* /etc/passwd changed in some way */ |
2622 | /* /etc/passwd changed in some way */ |
1776 | if (w->attr.st_nlink) |
2623 | if (w->attr.st_nlink) |
1777 | { |
2624 | { |
1778 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2625 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1779 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2626 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1780 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2627 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1781 | } |
2628 | } |
1782 | else |
2629 | else |
1783 | /* you shalt not abuse printf for puts */ |
2630 | /* you shalt not abuse printf for puts */ |
1784 | puts ("wow, /etc/passwd is not there, expect problems. " |
2631 | puts ("wow, /etc/passwd is not there, expect problems. " |
1785 | "if this is windows, they already arrived\n"); |
2632 | "if this is windows, they already arrived\n"); |
1786 | } |
2633 | } |
1787 | |
2634 | |
1788 | ... |
2635 | ... |
1789 | ev_stat passwd; |
2636 | ev_stat passwd; |
1790 | |
2637 | |
1791 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
2638 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1792 | ev_stat_start (loop, &passwd); |
2639 | ev_stat_start (loop, &passwd); |
1793 | |
2640 | |
1794 | Example: Like above, but additionally use a one-second delay so we do not |
2641 | Example: Like above, but additionally use a one-second delay so we do not |
1795 | miss updates (however, frequent updates will delay processing, too, so |
2642 | miss updates (however, frequent updates will delay processing, too, so |
1796 | one might do the work both on C<ev_stat> callback invocation I<and> on |
2643 | one might do the work both on C<ev_stat> callback invocation I<and> on |
1797 | C<ev_timer> callback invocation). |
2644 | C<ev_timer> callback invocation). |
1798 | |
2645 | |
1799 | static ev_stat passwd; |
2646 | static ev_stat passwd; |
1800 | static ev_timer timer; |
2647 | static ev_timer timer; |
1801 | |
2648 | |
1802 | static void |
2649 | static void |
1803 | timer_cb (EV_P_ ev_timer *w, int revents) |
2650 | timer_cb (EV_P_ ev_timer *w, int revents) |
1804 | { |
2651 | { |
1805 | ev_timer_stop (EV_A_ w); |
2652 | ev_timer_stop (EV_A_ w); |
1806 | |
2653 | |
1807 | /* now it's one second after the most recent passwd change */ |
2654 | /* now it's one second after the most recent passwd change */ |
1808 | } |
2655 | } |
1809 | |
2656 | |
1810 | static void |
2657 | static void |
1811 | stat_cb (EV_P_ ev_stat *w, int revents) |
2658 | stat_cb (EV_P_ ev_stat *w, int revents) |
1812 | { |
2659 | { |
1813 | /* reset the one-second timer */ |
2660 | /* reset the one-second timer */ |
1814 | ev_timer_again (EV_A_ &timer); |
2661 | ev_timer_again (EV_A_ &timer); |
1815 | } |
2662 | } |
1816 | |
2663 | |
1817 | ... |
2664 | ... |
1818 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2665 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1819 | ev_stat_start (loop, &passwd); |
2666 | ev_stat_start (loop, &passwd); |
1820 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
2667 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1821 | |
2668 | |
1822 | |
2669 | |
1823 | =head2 C<ev_idle> - when you've got nothing better to do... |
2670 | =head2 C<ev_idle> - when you've got nothing better to do... |
1824 | |
2671 | |
1825 | Idle watchers trigger events when no other events of the same or higher |
2672 | Idle watchers trigger events when no other events of the same or higher |
1826 | priority are pending (prepare, check and other idle watchers do not |
2673 | priority are pending (prepare, check and other idle watchers do not count |
1827 | count). |
2674 | as receiving "events"). |
1828 | |
2675 | |
1829 | That is, as long as your process is busy handling sockets or timeouts |
2676 | That is, as long as your process is busy handling sockets or timeouts |
1830 | (or even signals, imagine) of the same or higher priority it will not be |
2677 | (or even signals, imagine) of the same or higher priority it will not be |
1831 | triggered. But when your process is idle (or only lower-priority watchers |
2678 | triggered. But when your process is idle (or only lower-priority watchers |
1832 | are pending), the idle watchers are being called once per event loop |
2679 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1843 | |
2690 | |
1844 | =head3 Watcher-Specific Functions and Data Members |
2691 | =head3 Watcher-Specific Functions and Data Members |
1845 | |
2692 | |
1846 | =over 4 |
2693 | =over 4 |
1847 | |
2694 | |
1848 | =item ev_idle_init (ev_signal *, callback) |
2695 | =item ev_idle_init (ev_idle *, callback) |
1849 | |
2696 | |
1850 | Initialises and configures the idle watcher - it has no parameters of any |
2697 | Initialises and configures the idle watcher - it has no parameters of any |
1851 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2698 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1852 | believe me. |
2699 | believe me. |
1853 | |
2700 | |
… | |
… | |
1856 | =head3 Examples |
2703 | =head3 Examples |
1857 | |
2704 | |
1858 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2705 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1859 | callback, free it. Also, use no error checking, as usual. |
2706 | callback, free it. Also, use no error checking, as usual. |
1860 | |
2707 | |
1861 | static void |
2708 | static void |
1862 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2709 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1863 | { |
2710 | { |
1864 | free (w); |
2711 | free (w); |
1865 | // now do something you wanted to do when the program has |
2712 | // now do something you wanted to do when the program has |
1866 | // no longer anything immediate to do. |
2713 | // no longer anything immediate to do. |
1867 | } |
2714 | } |
1868 | |
2715 | |
1869 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2716 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1870 | ev_idle_init (idle_watcher, idle_cb); |
2717 | ev_idle_init (idle_watcher, idle_cb); |
1871 | ev_idle_start (loop, idle_cb); |
2718 | ev_idle_start (loop, idle_watcher); |
1872 | |
2719 | |
1873 | |
2720 | |
1874 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2721 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1875 | |
2722 | |
1876 | Prepare and check watchers are usually (but not always) used in tandem: |
2723 | Prepare and check watchers are usually (but not always) used in pairs: |
1877 | prepare watchers get invoked before the process blocks and check watchers |
2724 | prepare watchers get invoked before the process blocks and check watchers |
1878 | afterwards. |
2725 | afterwards. |
1879 | |
2726 | |
1880 | You I<must not> call C<ev_loop> or similar functions that enter |
2727 | You I<must not> call C<ev_run> or similar functions that enter |
1881 | the current event loop from either C<ev_prepare> or C<ev_check> |
2728 | the current event loop from either C<ev_prepare> or C<ev_check> |
1882 | watchers. Other loops than the current one are fine, however. The |
2729 | watchers. Other loops than the current one are fine, however. The |
1883 | rationale behind this is that you do not need to check for recursion in |
2730 | rationale behind this is that you do not need to check for recursion in |
1884 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2731 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1885 | C<ev_check> so if you have one watcher of each kind they will always be |
2732 | C<ev_check> so if you have one watcher of each kind they will always be |
1886 | called in pairs bracketing the blocking call. |
2733 | called in pairs bracketing the blocking call. |
1887 | |
2734 | |
1888 | Their main purpose is to integrate other event mechanisms into libev and |
2735 | Their main purpose is to integrate other event mechanisms into libev and |
1889 | their use is somewhat advanced. This could be used, for example, to track |
2736 | their use is somewhat advanced. They could be used, for example, to track |
1890 | variable changes, implement your own watchers, integrate net-snmp or a |
2737 | variable changes, implement your own watchers, integrate net-snmp or a |
1891 | coroutine library and lots more. They are also occasionally useful if |
2738 | coroutine library and lots more. They are also occasionally useful if |
1892 | you cache some data and want to flush it before blocking (for example, |
2739 | you cache some data and want to flush it before blocking (for example, |
1893 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2740 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1894 | watcher). |
2741 | watcher). |
1895 | |
2742 | |
1896 | This is done by examining in each prepare call which file descriptors need |
2743 | This is done by examining in each prepare call which file descriptors |
1897 | to be watched by the other library, registering C<ev_io> watchers for |
2744 | need to be watched by the other library, registering C<ev_io> watchers |
1898 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2745 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1899 | provide just this functionality). Then, in the check watcher you check for |
2746 | libraries provide exactly this functionality). Then, in the check watcher, |
1900 | any events that occurred (by checking the pending status of all watchers |
2747 | you check for any events that occurred (by checking the pending status |
1901 | and stopping them) and call back into the library. The I/O and timer |
2748 | of all watchers and stopping them) and call back into the library. The |
1902 | callbacks will never actually be called (but must be valid nevertheless, |
2749 | I/O and timer callbacks will never actually be called (but must be valid |
1903 | because you never know, you know?). |
2750 | nevertheless, because you never know, you know?). |
1904 | |
2751 | |
1905 | As another example, the Perl Coro module uses these hooks to integrate |
2752 | As another example, the Perl Coro module uses these hooks to integrate |
1906 | coroutines into libev programs, by yielding to other active coroutines |
2753 | coroutines into libev programs, by yielding to other active coroutines |
1907 | during each prepare and only letting the process block if no coroutines |
2754 | during each prepare and only letting the process block if no coroutines |
1908 | are ready to run (it's actually more complicated: it only runs coroutines |
2755 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1911 | loop from blocking if lower-priority coroutines are active, thus mapping |
2758 | loop from blocking if lower-priority coroutines are active, thus mapping |
1912 | low-priority coroutines to idle/background tasks). |
2759 | low-priority coroutines to idle/background tasks). |
1913 | |
2760 | |
1914 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2761 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1915 | priority, to ensure that they are being run before any other watchers |
2762 | priority, to ensure that they are being run before any other watchers |
|
|
2763 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2764 | |
1916 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2765 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1917 | too) should not activate ("feed") events into libev. While libev fully |
2766 | activate ("feed") events into libev. While libev fully supports this, they |
1918 | supports this, they might get executed before other C<ev_check> watchers |
2767 | might get executed before other C<ev_check> watchers did their job. As |
1919 | did their job. As C<ev_check> watchers are often used to embed other |
2768 | C<ev_check> watchers are often used to embed other (non-libev) event |
1920 | (non-libev) event loops those other event loops might be in an unusable |
2769 | loops those other event loops might be in an unusable state until their |
1921 | state until their C<ev_check> watcher ran (always remind yourself to |
2770 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1922 | coexist peacefully with others). |
2771 | others). |
1923 | |
2772 | |
1924 | =head3 Watcher-Specific Functions and Data Members |
2773 | =head3 Watcher-Specific Functions and Data Members |
1925 | |
2774 | |
1926 | =over 4 |
2775 | =over 4 |
1927 | |
2776 | |
… | |
… | |
1929 | |
2778 | |
1930 | =item ev_check_init (ev_check *, callback) |
2779 | =item ev_check_init (ev_check *, callback) |
1931 | |
2780 | |
1932 | Initialises and configures the prepare or check watcher - they have no |
2781 | Initialises and configures the prepare or check watcher - they have no |
1933 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2782 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1934 | macros, but using them is utterly, utterly and completely pointless. |
2783 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2784 | pointless. |
1935 | |
2785 | |
1936 | =back |
2786 | =back |
1937 | |
2787 | |
1938 | =head3 Examples |
2788 | =head3 Examples |
1939 | |
2789 | |
… | |
… | |
1948 | and in a check watcher, destroy them and call into libadns. What follows |
2798 | and in a check watcher, destroy them and call into libadns. What follows |
1949 | is pseudo-code only of course. This requires you to either use a low |
2799 | is pseudo-code only of course. This requires you to either use a low |
1950 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
2800 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1951 | the callbacks for the IO/timeout watchers might not have been called yet. |
2801 | the callbacks for the IO/timeout watchers might not have been called yet. |
1952 | |
2802 | |
1953 | static ev_io iow [nfd]; |
2803 | static ev_io iow [nfd]; |
1954 | static ev_timer tw; |
2804 | static ev_timer tw; |
1955 | |
2805 | |
1956 | static void |
2806 | static void |
1957 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2807 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1958 | { |
2808 | { |
1959 | } |
2809 | } |
1960 | |
2810 | |
1961 | // create io watchers for each fd and a timer before blocking |
2811 | // create io watchers for each fd and a timer before blocking |
1962 | static void |
2812 | static void |
1963 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2813 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1964 | { |
2814 | { |
1965 | int timeout = 3600000; |
2815 | int timeout = 3600000; |
1966 | struct pollfd fds [nfd]; |
2816 | struct pollfd fds [nfd]; |
1967 | // actual code will need to loop here and realloc etc. |
2817 | // actual code will need to loop here and realloc etc. |
1968 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2818 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1969 | |
2819 | |
1970 | /* the callback is illegal, but won't be called as we stop during check */ |
2820 | /* the callback is illegal, but won't be called as we stop during check */ |
1971 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2821 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1972 | ev_timer_start (loop, &tw); |
2822 | ev_timer_start (loop, &tw); |
1973 | |
2823 | |
1974 | // create one ev_io per pollfd |
2824 | // create one ev_io per pollfd |
1975 | for (int i = 0; i < nfd; ++i) |
2825 | for (int i = 0; i < nfd; ++i) |
1976 | { |
2826 | { |
1977 | ev_io_init (iow + i, io_cb, fds [i].fd, |
2827 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1978 | ((fds [i].events & POLLIN ? EV_READ : 0) |
2828 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1979 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2829 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1980 | |
2830 | |
1981 | fds [i].revents = 0; |
2831 | fds [i].revents = 0; |
1982 | ev_io_start (loop, iow + i); |
2832 | ev_io_start (loop, iow + i); |
1983 | } |
2833 | } |
1984 | } |
2834 | } |
1985 | |
2835 | |
1986 | // stop all watchers after blocking |
2836 | // stop all watchers after blocking |
1987 | static void |
2837 | static void |
1988 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2838 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1989 | { |
2839 | { |
1990 | ev_timer_stop (loop, &tw); |
2840 | ev_timer_stop (loop, &tw); |
1991 | |
2841 | |
1992 | for (int i = 0; i < nfd; ++i) |
2842 | for (int i = 0; i < nfd; ++i) |
1993 | { |
2843 | { |
1994 | // set the relevant poll flags |
2844 | // set the relevant poll flags |
1995 | // could also call adns_processreadable etc. here |
2845 | // could also call adns_processreadable etc. here |
1996 | struct pollfd *fd = fds + i; |
2846 | struct pollfd *fd = fds + i; |
1997 | int revents = ev_clear_pending (iow + i); |
2847 | int revents = ev_clear_pending (iow + i); |
1998 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
2848 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1999 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
2849 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
2000 | |
2850 | |
2001 | // now stop the watcher |
2851 | // now stop the watcher |
2002 | ev_io_stop (loop, iow + i); |
2852 | ev_io_stop (loop, iow + i); |
2003 | } |
2853 | } |
2004 | |
2854 | |
2005 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2855 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2006 | } |
2856 | } |
2007 | |
2857 | |
2008 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
2858 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
2009 | in the prepare watcher and would dispose of the check watcher. |
2859 | in the prepare watcher and would dispose of the check watcher. |
2010 | |
2860 | |
2011 | Method 3: If the module to be embedded supports explicit event |
2861 | Method 3: If the module to be embedded supports explicit event |
2012 | notification (libadns does), you can also make use of the actual watcher |
2862 | notification (libadns does), you can also make use of the actual watcher |
2013 | callbacks, and only destroy/create the watchers in the prepare watcher. |
2863 | callbacks, and only destroy/create the watchers in the prepare watcher. |
2014 | |
2864 | |
2015 | static void |
2865 | static void |
2016 | timer_cb (EV_P_ ev_timer *w, int revents) |
2866 | timer_cb (EV_P_ ev_timer *w, int revents) |
2017 | { |
2867 | { |
2018 | adns_state ads = (adns_state)w->data; |
2868 | adns_state ads = (adns_state)w->data; |
2019 | update_now (EV_A); |
2869 | update_now (EV_A); |
2020 | |
2870 | |
2021 | adns_processtimeouts (ads, &tv_now); |
2871 | adns_processtimeouts (ads, &tv_now); |
2022 | } |
2872 | } |
2023 | |
2873 | |
2024 | static void |
2874 | static void |
2025 | io_cb (EV_P_ ev_io *w, int revents) |
2875 | io_cb (EV_P_ ev_io *w, int revents) |
2026 | { |
2876 | { |
2027 | adns_state ads = (adns_state)w->data; |
2877 | adns_state ads = (adns_state)w->data; |
2028 | update_now (EV_A); |
2878 | update_now (EV_A); |
2029 | |
2879 | |
2030 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
2880 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
2031 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
2881 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
2032 | } |
2882 | } |
2033 | |
2883 | |
2034 | // do not ever call adns_afterpoll |
2884 | // do not ever call adns_afterpoll |
2035 | |
2885 | |
2036 | Method 4: Do not use a prepare or check watcher because the module you |
2886 | Method 4: Do not use a prepare or check watcher because the module you |
2037 | want to embed is too inflexible to support it. Instead, you can override |
2887 | want to embed is not flexible enough to support it. Instead, you can |
2038 | their poll function. The drawback with this solution is that the main |
2888 | override their poll function. The drawback with this solution is that the |
2039 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2889 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2040 | this. |
2890 | this approach, effectively embedding EV as a client into the horrible |
|
|
2891 | libglib event loop. |
2041 | |
2892 | |
2042 | static gint |
2893 | static gint |
2043 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2894 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2044 | { |
2895 | { |
2045 | int got_events = 0; |
2896 | int got_events = 0; |
2046 | |
2897 | |
2047 | for (n = 0; n < nfds; ++n) |
2898 | for (n = 0; n < nfds; ++n) |
2048 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2899 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2049 | |
2900 | |
2050 | if (timeout >= 0) |
2901 | if (timeout >= 0) |
2051 | // create/start timer |
2902 | // create/start timer |
2052 | |
2903 | |
2053 | // poll |
2904 | // poll |
2054 | ev_loop (EV_A_ 0); |
2905 | ev_run (EV_A_ 0); |
2055 | |
2906 | |
2056 | // stop timer again |
2907 | // stop timer again |
2057 | if (timeout >= 0) |
2908 | if (timeout >= 0) |
2058 | ev_timer_stop (EV_A_ &to); |
2909 | ev_timer_stop (EV_A_ &to); |
2059 | |
2910 | |
2060 | // stop io watchers again - their callbacks should have set |
2911 | // stop io watchers again - their callbacks should have set |
2061 | for (n = 0; n < nfds; ++n) |
2912 | for (n = 0; n < nfds; ++n) |
2062 | ev_io_stop (EV_A_ iow [n]); |
2913 | ev_io_stop (EV_A_ iow [n]); |
2063 | |
2914 | |
2064 | return got_events; |
2915 | return got_events; |
2065 | } |
2916 | } |
2066 | |
2917 | |
2067 | |
2918 | |
2068 | =head2 C<ev_embed> - when one backend isn't enough... |
2919 | =head2 C<ev_embed> - when one backend isn't enough... |
2069 | |
2920 | |
2070 | This is a rather advanced watcher type that lets you embed one event loop |
2921 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
2076 | prioritise I/O. |
2927 | prioritise I/O. |
2077 | |
2928 | |
2078 | As an example for a bug workaround, the kqueue backend might only support |
2929 | As an example for a bug workaround, the kqueue backend might only support |
2079 | sockets on some platform, so it is unusable as generic backend, but you |
2930 | sockets on some platform, so it is unusable as generic backend, but you |
2080 | still want to make use of it because you have many sockets and it scales |
2931 | still want to make use of it because you have many sockets and it scales |
2081 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2932 | so nicely. In this case, you would create a kqueue-based loop and embed |
2082 | into your default loop (which might use e.g. poll). Overall operation will |
2933 | it into your default loop (which might use e.g. poll). Overall operation |
2083 | be a bit slower because first libev has to poll and then call kevent, but |
2934 | will be a bit slower because first libev has to call C<poll> and then |
2084 | at least you can use both at what they are best. |
2935 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2936 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2085 | |
2937 | |
2086 | As for prioritising I/O: rarely you have the case where some fds have |
2938 | As for prioritising I/O: under rare circumstances you have the case where |
2087 | to be watched and handled very quickly (with low latency), and even |
2939 | some fds have to be watched and handled very quickly (with low latency), |
2088 | priorities and idle watchers might have too much overhead. In this case |
2940 | and even priorities and idle watchers might have too much overhead. In |
2089 | you would put all the high priority stuff in one loop and all the rest in |
2941 | this case you would put all the high priority stuff in one loop and all |
2090 | a second one, and embed the second one in the first. |
2942 | the rest in a second one, and embed the second one in the first. |
2091 | |
2943 | |
2092 | As long as the watcher is active, the callback will be invoked every time |
2944 | As long as the watcher is active, the callback will be invoked every |
2093 | there might be events pending in the embedded loop. The callback must then |
2945 | time there might be events pending in the embedded loop. The callback |
2094 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2946 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2095 | their callbacks (you could also start an idle watcher to give the embedded |
2947 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2096 | loop strictly lower priority for example). You can also set the callback |
2948 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2097 | to C<0>, in which case the embed watcher will automatically execute the |
2949 | to give the embedded loop strictly lower priority for example). |
2098 | embedded loop sweep. |
|
|
2099 | |
2950 | |
2100 | As long as the watcher is started it will automatically handle events. The |
2951 | You can also set the callback to C<0>, in which case the embed watcher |
2101 | callback will be invoked whenever some events have been handled. You can |
2952 | will automatically execute the embedded loop sweep whenever necessary. |
2102 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2103 | interested in that. |
|
|
2104 | |
2953 | |
2105 | Also, there have not currently been made special provisions for forking: |
2954 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2106 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2955 | is active, i.e., the embedded loop will automatically be forked when the |
2107 | but you will also have to stop and restart any C<ev_embed> watchers |
2956 | embedding loop forks. In other cases, the user is responsible for calling |
2108 | yourself. |
2957 | C<ev_loop_fork> on the embedded loop. |
2109 | |
2958 | |
2110 | Unfortunately, not all backends are embeddable, only the ones returned by |
2959 | Unfortunately, not all backends are embeddable: only the ones returned by |
2111 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2960 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2112 | portable one. |
2961 | portable one. |
2113 | |
2962 | |
2114 | So when you want to use this feature you will always have to be prepared |
2963 | So when you want to use this feature you will always have to be prepared |
2115 | that you cannot get an embeddable loop. The recommended way to get around |
2964 | that you cannot get an embeddable loop. The recommended way to get around |
2116 | this is to have a separate variables for your embeddable loop, try to |
2965 | this is to have a separate variables for your embeddable loop, try to |
2117 | create it, and if that fails, use the normal loop for everything. |
2966 | create it, and if that fails, use the normal loop for everything. |
|
|
2967 | |
|
|
2968 | =head3 C<ev_embed> and fork |
|
|
2969 | |
|
|
2970 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2971 | automatically be applied to the embedded loop as well, so no special |
|
|
2972 | fork handling is required in that case. When the watcher is not running, |
|
|
2973 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2974 | as applicable. |
2118 | |
2975 | |
2119 | =head3 Watcher-Specific Functions and Data Members |
2976 | =head3 Watcher-Specific Functions and Data Members |
2120 | |
2977 | |
2121 | =over 4 |
2978 | =over 4 |
2122 | |
2979 | |
… | |
… | |
2131 | if you do not want that, you need to temporarily stop the embed watcher). |
2988 | if you do not want that, you need to temporarily stop the embed watcher). |
2132 | |
2989 | |
2133 | =item ev_embed_sweep (loop, ev_embed *) |
2990 | =item ev_embed_sweep (loop, ev_embed *) |
2134 | |
2991 | |
2135 | Make a single, non-blocking sweep over the embedded loop. This works |
2992 | Make a single, non-blocking sweep over the embedded loop. This works |
2136 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2993 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2137 | appropriate way for embedded loops. |
2994 | appropriate way for embedded loops. |
2138 | |
2995 | |
2139 | =item struct ev_loop *other [read-only] |
2996 | =item struct ev_loop *other [read-only] |
2140 | |
2997 | |
2141 | The embedded event loop. |
2998 | The embedded event loop. |
… | |
… | |
2148 | event loop. If that is not possible, use the default loop. The default |
3005 | event loop. If that is not possible, use the default loop. The default |
2149 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
3006 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
2150 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
3007 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2151 | used). |
3008 | used). |
2152 | |
3009 | |
2153 | struct ev_loop *loop_hi = ev_default_init (0); |
3010 | struct ev_loop *loop_hi = ev_default_init (0); |
2154 | struct ev_loop *loop_lo = 0; |
3011 | struct ev_loop *loop_lo = 0; |
2155 | struct ev_embed embed; |
3012 | ev_embed embed; |
2156 | |
3013 | |
2157 | // see if there is a chance of getting one that works |
3014 | // see if there is a chance of getting one that works |
2158 | // (remember that a flags value of 0 means autodetection) |
3015 | // (remember that a flags value of 0 means autodetection) |
2159 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3016 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2160 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3017 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2161 | : 0; |
3018 | : 0; |
2162 | |
3019 | |
2163 | // if we got one, then embed it, otherwise default to loop_hi |
3020 | // if we got one, then embed it, otherwise default to loop_hi |
2164 | if (loop_lo) |
3021 | if (loop_lo) |
2165 | { |
3022 | { |
2166 | ev_embed_init (&embed, 0, loop_lo); |
3023 | ev_embed_init (&embed, 0, loop_lo); |
2167 | ev_embed_start (loop_hi, &embed); |
3024 | ev_embed_start (loop_hi, &embed); |
2168 | } |
3025 | } |
2169 | else |
3026 | else |
2170 | loop_lo = loop_hi; |
3027 | loop_lo = loop_hi; |
2171 | |
3028 | |
2172 | Example: Check if kqueue is available but not recommended and create |
3029 | Example: Check if kqueue is available but not recommended and create |
2173 | a kqueue backend for use with sockets (which usually work with any |
3030 | a kqueue backend for use with sockets (which usually work with any |
2174 | kqueue implementation). Store the kqueue/socket-only event loop in |
3031 | kqueue implementation). Store the kqueue/socket-only event loop in |
2175 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3032 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2176 | |
3033 | |
2177 | struct ev_loop *loop = ev_default_init (0); |
3034 | struct ev_loop *loop = ev_default_init (0); |
2178 | struct ev_loop *loop_socket = 0; |
3035 | struct ev_loop *loop_socket = 0; |
2179 | struct ev_embed embed; |
3036 | ev_embed embed; |
2180 | |
3037 | |
2181 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3038 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2182 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3039 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2183 | { |
3040 | { |
2184 | ev_embed_init (&embed, 0, loop_socket); |
3041 | ev_embed_init (&embed, 0, loop_socket); |
2185 | ev_embed_start (loop, &embed); |
3042 | ev_embed_start (loop, &embed); |
2186 | } |
3043 | } |
2187 | |
3044 | |
2188 | if (!loop_socket) |
3045 | if (!loop_socket) |
2189 | loop_socket = loop; |
3046 | loop_socket = loop; |
2190 | |
3047 | |
2191 | // now use loop_socket for all sockets, and loop for everything else |
3048 | // now use loop_socket for all sockets, and loop for everything else |
2192 | |
3049 | |
2193 | |
3050 | |
2194 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3051 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2195 | |
3052 | |
2196 | Fork watchers are called when a C<fork ()> was detected (usually because |
3053 | Fork watchers are called when a C<fork ()> was detected (usually because |
… | |
… | |
2199 | event loop blocks next and before C<ev_check> watchers are being called, |
3056 | event loop blocks next and before C<ev_check> watchers are being called, |
2200 | and only in the child after the fork. If whoever good citizen calling |
3057 | and only in the child after the fork. If whoever good citizen calling |
2201 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3058 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2202 | handlers will be invoked, too, of course. |
3059 | handlers will be invoked, too, of course. |
2203 | |
3060 | |
|
|
3061 | =head3 The special problem of life after fork - how is it possible? |
|
|
3062 | |
|
|
3063 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3064 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3065 | sequence should be handled by libev without any problems. |
|
|
3066 | |
|
|
3067 | This changes when the application actually wants to do event handling |
|
|
3068 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3069 | fork. |
|
|
3070 | |
|
|
3071 | The default mode of operation (for libev, with application help to detect |
|
|
3072 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3073 | when I<either> the parent I<or> the child process continues. |
|
|
3074 | |
|
|
3075 | When both processes want to continue using libev, then this is usually the |
|
|
3076 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3077 | supposed to continue with all watchers in place as before, while the other |
|
|
3078 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3079 | |
|
|
3080 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3081 | simply create a new event loop, which of course will be "empty", and |
|
|
3082 | use that for new watchers. This has the advantage of not touching more |
|
|
3083 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3084 | disadvantage of having to use multiple event loops (which do not support |
|
|
3085 | signal watchers). |
|
|
3086 | |
|
|
3087 | When this is not possible, or you want to use the default loop for |
|
|
3088 | other reasons, then in the process that wants to start "fresh", call |
|
|
3089 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3090 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3091 | watchers, so you have to be careful not to execute code that modifies |
|
|
3092 | those watchers. Note also that in that case, you have to re-register any |
|
|
3093 | signal watchers. |
|
|
3094 | |
2204 | =head3 Watcher-Specific Functions and Data Members |
3095 | =head3 Watcher-Specific Functions and Data Members |
2205 | |
3096 | |
2206 | =over 4 |
3097 | =over 4 |
2207 | |
3098 | |
2208 | =item ev_fork_init (ev_signal *, callback) |
3099 | =item ev_fork_init (ev_fork *, callback) |
2209 | |
3100 | |
2210 | Initialises and configures the fork watcher - it has no parameters of any |
3101 | Initialises and configures the fork watcher - it has no parameters of any |
2211 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3102 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2212 | believe me. |
3103 | believe me. |
2213 | |
3104 | |
2214 | =back |
3105 | =back |
2215 | |
3106 | |
2216 | |
3107 | |
|
|
3108 | =head2 C<ev_cleanup> - even the best things end |
|
|
3109 | |
|
|
3110 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3111 | by a call to C<ev_loop_destroy>. |
|
|
3112 | |
|
|
3113 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3114 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3115 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3116 | loop when you want them to be invoked. |
|
|
3117 | |
|
|
3118 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3119 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3120 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3121 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3122 | |
|
|
3123 | =head3 Watcher-Specific Functions and Data Members |
|
|
3124 | |
|
|
3125 | =over 4 |
|
|
3126 | |
|
|
3127 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3128 | |
|
|
3129 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3130 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3131 | pointless, believe me. |
|
|
3132 | |
|
|
3133 | =back |
|
|
3134 | |
|
|
3135 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3136 | cleanup functions are called. |
|
|
3137 | |
|
|
3138 | static void |
|
|
3139 | program_exits (void) |
|
|
3140 | { |
|
|
3141 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3142 | } |
|
|
3143 | |
|
|
3144 | ... |
|
|
3145 | atexit (program_exits); |
|
|
3146 | |
|
|
3147 | |
2217 | =head2 C<ev_async> - how to wake up another event loop |
3148 | =head2 C<ev_async> - how to wake up an event loop |
2218 | |
3149 | |
2219 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3150 | In general, you cannot use an C<ev_run> from multiple threads or other |
2220 | asynchronous sources such as signal handlers (as opposed to multiple event |
3151 | asynchronous sources such as signal handlers (as opposed to multiple event |
2221 | loops - those are of course safe to use in different threads). |
3152 | loops - those are of course safe to use in different threads). |
2222 | |
3153 | |
2223 | Sometimes, however, you need to wake up another event loop you do not |
3154 | Sometimes, however, you need to wake up an event loop you do not control, |
2224 | control, for example because it belongs to another thread. This is what |
3155 | for example because it belongs to another thread. This is what C<ev_async> |
2225 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3156 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2226 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3157 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2227 | safe. |
|
|
2228 | |
3158 | |
2229 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3159 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2230 | too, are asynchronous in nature, and signals, too, will be compressed |
3160 | too, are asynchronous in nature, and signals, too, will be compressed |
2231 | (i.e. the number of callback invocations may be less than the number of |
3161 | (i.e. the number of callback invocations may be less than the number of |
2232 | C<ev_async_sent> calls). |
3162 | C<ev_async_sent> calls). |
… | |
… | |
2237 | =head3 Queueing |
3167 | =head3 Queueing |
2238 | |
3168 | |
2239 | C<ev_async> does not support queueing of data in any way. The reason |
3169 | C<ev_async> does not support queueing of data in any way. The reason |
2240 | is that the author does not know of a simple (or any) algorithm for a |
3170 | is that the author does not know of a simple (or any) algorithm for a |
2241 | multiple-writer-single-reader queue that works in all cases and doesn't |
3171 | multiple-writer-single-reader queue that works in all cases and doesn't |
2242 | need elaborate support such as pthreads. |
3172 | need elaborate support such as pthreads or unportable memory access |
|
|
3173 | semantics. |
2243 | |
3174 | |
2244 | That means that if you want to queue data, you have to provide your own |
3175 | That means that if you want to queue data, you have to provide your own |
2245 | queue. But at least I can tell you would implement locking around your |
3176 | queue. But at least I can tell you how to implement locking around your |
2246 | queue: |
3177 | queue: |
2247 | |
3178 | |
2248 | =over 4 |
3179 | =over 4 |
2249 | |
3180 | |
2250 | =item queueing from a signal handler context |
3181 | =item queueing from a signal handler context |
2251 | |
3182 | |
2252 | To implement race-free queueing, you simply add to the queue in the signal |
3183 | To implement race-free queueing, you simply add to the queue in the signal |
2253 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3184 | handler but you block the signal handler in the watcher callback. Here is |
2254 | some fictitious SIGUSR1 handler: |
3185 | an example that does that for some fictitious SIGUSR1 handler: |
2255 | |
3186 | |
2256 | static ev_async mysig; |
3187 | static ev_async mysig; |
2257 | |
3188 | |
2258 | static void |
3189 | static void |
2259 | sigusr1_handler (void) |
3190 | sigusr1_handler (void) |
… | |
… | |
2325 | =over 4 |
3256 | =over 4 |
2326 | |
3257 | |
2327 | =item ev_async_init (ev_async *, callback) |
3258 | =item ev_async_init (ev_async *, callback) |
2328 | |
3259 | |
2329 | Initialises and configures the async watcher - it has no parameters of any |
3260 | Initialises and configures the async watcher - it has no parameters of any |
2330 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3261 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2331 | believe me. |
3262 | trust me. |
2332 | |
3263 | |
2333 | =item ev_async_send (loop, ev_async *) |
3264 | =item ev_async_send (loop, ev_async *) |
2334 | |
3265 | |
2335 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3266 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2336 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3267 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2337 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3268 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2338 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3269 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2339 | section below on what exactly this means). |
3270 | section below on what exactly this means). |
2340 | |
3271 | |
|
|
3272 | Note that, as with other watchers in libev, multiple events might get |
|
|
3273 | compressed into a single callback invocation (another way to look at this |
|
|
3274 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3275 | reset when the event loop detects that). |
|
|
3276 | |
2341 | This call incurs the overhead of a system call only once per loop iteration, |
3277 | This call incurs the overhead of a system call only once per event loop |
2342 | so while the overhead might be noticeable, it doesn't apply to repeated |
3278 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2343 | calls to C<ev_async_send>. |
3279 | repeated calls to C<ev_async_send> for the same event loop. |
2344 | |
3280 | |
2345 | =item bool = ev_async_pending (ev_async *) |
3281 | =item bool = ev_async_pending (ev_async *) |
2346 | |
3282 | |
2347 | Returns a non-zero value when C<ev_async_send> has been called on the |
3283 | Returns a non-zero value when C<ev_async_send> has been called on the |
2348 | watcher but the event has not yet been processed (or even noted) by the |
3284 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2351 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3287 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2352 | the loop iterates next and checks for the watcher to have become active, |
3288 | the loop iterates next and checks for the watcher to have become active, |
2353 | it will reset the flag again. C<ev_async_pending> can be used to very |
3289 | it will reset the flag again. C<ev_async_pending> can be used to very |
2354 | quickly check whether invoking the loop might be a good idea. |
3290 | quickly check whether invoking the loop might be a good idea. |
2355 | |
3291 | |
2356 | Not that this does I<not> check whether the watcher itself is pending, only |
3292 | Not that this does I<not> check whether the watcher itself is pending, |
2357 | whether it has been requested to make this watcher pending. |
3293 | only whether it has been requested to make this watcher pending: there |
|
|
3294 | is a time window between the event loop checking and resetting the async |
|
|
3295 | notification, and the callback being invoked. |
2358 | |
3296 | |
2359 | =back |
3297 | =back |
2360 | |
3298 | |
2361 | |
3299 | |
2362 | =head1 OTHER FUNCTIONS |
3300 | =head1 OTHER FUNCTIONS |
… | |
… | |
2366 | =over 4 |
3304 | =over 4 |
2367 | |
3305 | |
2368 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3306 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2369 | |
3307 | |
2370 | This function combines a simple timer and an I/O watcher, calls your |
3308 | This function combines a simple timer and an I/O watcher, calls your |
2371 | callback on whichever event happens first and automatically stop both |
3309 | callback on whichever event happens first and automatically stops both |
2372 | watchers. This is useful if you want to wait for a single event on an fd |
3310 | watchers. This is useful if you want to wait for a single event on an fd |
2373 | or timeout without having to allocate/configure/start/stop/free one or |
3311 | or timeout without having to allocate/configure/start/stop/free one or |
2374 | more watchers yourself. |
3312 | more watchers yourself. |
2375 | |
3313 | |
2376 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3314 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2377 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3315 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2378 | C<events> set will be created and started. |
3316 | the given C<fd> and C<events> set will be created and started. |
2379 | |
3317 | |
2380 | If C<timeout> is less than 0, then no timeout watcher will be |
3318 | If C<timeout> is less than 0, then no timeout watcher will be |
2381 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3319 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2382 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3320 | repeat = 0) will be started. C<0> is a valid timeout. |
2383 | dubious value. |
|
|
2384 | |
3321 | |
2385 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3322 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2386 | passed an C<revents> set like normal event callbacks (a combination of |
3323 | passed an C<revents> set like normal event callbacks (a combination of |
2387 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3324 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2388 | value passed to C<ev_once>: |
3325 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3326 | a timeout and an io event at the same time - you probably should give io |
|
|
3327 | events precedence. |
2389 | |
3328 | |
|
|
3329 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
3330 | |
2390 | static void stdin_ready (int revents, void *arg) |
3331 | static void stdin_ready (int revents, void *arg) |
2391 | { |
3332 | { |
2392 | if (revents & EV_TIMEOUT) |
|
|
2393 | /* doh, nothing entered */; |
|
|
2394 | else if (revents & EV_READ) |
3333 | if (revents & EV_READ) |
2395 | /* stdin might have data for us, joy! */; |
3334 | /* stdin might have data for us, joy! */; |
|
|
3335 | else if (revents & EV_TIMER) |
|
|
3336 | /* doh, nothing entered */; |
2396 | } |
3337 | } |
2397 | |
3338 | |
2398 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3339 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2399 | |
3340 | |
2400 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2401 | |
|
|
2402 | Feeds the given event set into the event loop, as if the specified event |
|
|
2403 | had happened for the specified watcher (which must be a pointer to an |
|
|
2404 | initialised but not necessarily started event watcher). |
|
|
2405 | |
|
|
2406 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3341 | =item ev_feed_fd_event (loop, int fd, int revents) |
2407 | |
3342 | |
2408 | Feed an event on the given fd, as if a file descriptor backend detected |
3343 | Feed an event on the given fd, as if a file descriptor backend detected |
2409 | the given events it. |
3344 | the given events it. |
2410 | |
3345 | |
2411 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3346 | =item ev_feed_signal_event (loop, int signum) |
2412 | |
3347 | |
2413 | Feed an event as if the given signal occurred (C<loop> must be the default |
3348 | Feed an event as if the given signal occurred (C<loop> must be the default |
2414 | loop!). |
3349 | loop!). |
2415 | |
3350 | |
2416 | =back |
3351 | =back |
… | |
… | |
2452 | you to use some convenience methods to start/stop watchers and also change |
3387 | you to use some convenience methods to start/stop watchers and also change |
2453 | the callback model to a model using method callbacks on objects. |
3388 | the callback model to a model using method callbacks on objects. |
2454 | |
3389 | |
2455 | To use it, |
3390 | To use it, |
2456 | |
3391 | |
2457 | #include <ev++.h> |
3392 | #include <ev++.h> |
2458 | |
3393 | |
2459 | This automatically includes F<ev.h> and puts all of its definitions (many |
3394 | This automatically includes F<ev.h> and puts all of its definitions (many |
2460 | of them macros) into the global namespace. All C++ specific things are |
3395 | of them macros) into the global namespace. All C++ specific things are |
2461 | put into the C<ev> namespace. It should support all the same embedding |
3396 | put into the C<ev> namespace. It should support all the same embedding |
2462 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
3397 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
2496 | |
3431 | |
2497 | =over 4 |
3432 | =over 4 |
2498 | |
3433 | |
2499 | =item ev::TYPE::TYPE () |
3434 | =item ev::TYPE::TYPE () |
2500 | |
3435 | |
2501 | =item ev::TYPE::TYPE (struct ev_loop *) |
3436 | =item ev::TYPE::TYPE (loop) |
2502 | |
3437 | |
2503 | =item ev::TYPE::~TYPE |
3438 | =item ev::TYPE::~TYPE |
2504 | |
3439 | |
2505 | The constructor (optionally) takes an event loop to associate the watcher |
3440 | The constructor (optionally) takes an event loop to associate the watcher |
2506 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3441 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2529 | your compiler is good :), then the method will be fully inlined into the |
3464 | your compiler is good :), then the method will be fully inlined into the |
2530 | thunking function, making it as fast as a direct C callback. |
3465 | thunking function, making it as fast as a direct C callback. |
2531 | |
3466 | |
2532 | Example: simple class declaration and watcher initialisation |
3467 | Example: simple class declaration and watcher initialisation |
2533 | |
3468 | |
2534 | struct myclass |
3469 | struct myclass |
2535 | { |
3470 | { |
2536 | void io_cb (ev::io &w, int revents) { } |
3471 | void io_cb (ev::io &w, int revents) { } |
2537 | } |
3472 | } |
2538 | |
3473 | |
2539 | myclass obj; |
3474 | myclass obj; |
2540 | ev::io iow; |
3475 | ev::io iow; |
2541 | iow.set <myclass, &myclass::io_cb> (&obj); |
3476 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3477 | |
|
|
3478 | =item w->set (object *) |
|
|
3479 | |
|
|
3480 | This is a variation of a method callback - leaving out the method to call |
|
|
3481 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3482 | functor objects without having to manually specify the C<operator ()> all |
|
|
3483 | the time. Incidentally, you can then also leave out the template argument |
|
|
3484 | list. |
|
|
3485 | |
|
|
3486 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3487 | int revents)>. |
|
|
3488 | |
|
|
3489 | See the method-C<set> above for more details. |
|
|
3490 | |
|
|
3491 | Example: use a functor object as callback. |
|
|
3492 | |
|
|
3493 | struct myfunctor |
|
|
3494 | { |
|
|
3495 | void operator() (ev::io &w, int revents) |
|
|
3496 | { |
|
|
3497 | ... |
|
|
3498 | } |
|
|
3499 | } |
|
|
3500 | |
|
|
3501 | myfunctor f; |
|
|
3502 | |
|
|
3503 | ev::io w; |
|
|
3504 | w.set (&f); |
2542 | |
3505 | |
2543 | =item w->set<function> (void *data = 0) |
3506 | =item w->set<function> (void *data = 0) |
2544 | |
3507 | |
2545 | Also sets a callback, but uses a static method or plain function as |
3508 | Also sets a callback, but uses a static method or plain function as |
2546 | callback. The optional C<data> argument will be stored in the watcher's |
3509 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2548 | |
3511 | |
2549 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3512 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2550 | |
3513 | |
2551 | See the method-C<set> above for more details. |
3514 | See the method-C<set> above for more details. |
2552 | |
3515 | |
2553 | Example: |
3516 | Example: Use a plain function as callback. |
2554 | |
3517 | |
2555 | static void io_cb (ev::io &w, int revents) { } |
3518 | static void io_cb (ev::io &w, int revents) { } |
2556 | iow.set <io_cb> (); |
3519 | iow.set <io_cb> (); |
2557 | |
3520 | |
2558 | =item w->set (struct ev_loop *) |
3521 | =item w->set (loop) |
2559 | |
3522 | |
2560 | Associates a different C<struct ev_loop> with this watcher. You can only |
3523 | Associates a different C<struct ev_loop> with this watcher. You can only |
2561 | do this when the watcher is inactive (and not pending either). |
3524 | do this when the watcher is inactive (and not pending either). |
2562 | |
3525 | |
2563 | =item w->set ([arguments]) |
3526 | =item w->set ([arguments]) |
2564 | |
3527 | |
2565 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3528 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2566 | called at least once. Unlike the C counterpart, an active watcher gets |
3529 | method or a suitable start method must be called at least once. Unlike the |
2567 | automatically stopped and restarted when reconfiguring it with this |
3530 | C counterpart, an active watcher gets automatically stopped and restarted |
2568 | method. |
3531 | when reconfiguring it with this method. |
2569 | |
3532 | |
2570 | =item w->start () |
3533 | =item w->start () |
2571 | |
3534 | |
2572 | Starts the watcher. Note that there is no C<loop> argument, as the |
3535 | Starts the watcher. Note that there is no C<loop> argument, as the |
2573 | constructor already stores the event loop. |
3536 | constructor already stores the event loop. |
2574 | |
3537 | |
|
|
3538 | =item w->start ([arguments]) |
|
|
3539 | |
|
|
3540 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3541 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3542 | the configure C<set> method of the watcher. |
|
|
3543 | |
2575 | =item w->stop () |
3544 | =item w->stop () |
2576 | |
3545 | |
2577 | Stops the watcher if it is active. Again, no C<loop> argument. |
3546 | Stops the watcher if it is active. Again, no C<loop> argument. |
2578 | |
3547 | |
2579 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3548 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2591 | |
3560 | |
2592 | =back |
3561 | =back |
2593 | |
3562 | |
2594 | =back |
3563 | =back |
2595 | |
3564 | |
2596 | Example: Define a class with an IO and idle watcher, start one of them in |
3565 | Example: Define a class with two I/O and idle watchers, start the I/O |
2597 | the constructor. |
3566 | watchers in the constructor. |
2598 | |
3567 | |
2599 | class myclass |
3568 | class myclass |
2600 | { |
3569 | { |
2601 | ev::io io; void io_cb (ev::io &w, int revents); |
3570 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3571 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2602 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3572 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2603 | |
3573 | |
2604 | myclass (int fd) |
3574 | myclass (int fd) |
2605 | { |
3575 | { |
2606 | io .set <myclass, &myclass::io_cb > (this); |
3576 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3577 | io2 .set <myclass, &myclass::io2_cb > (this); |
2607 | idle.set <myclass, &myclass::idle_cb> (this); |
3578 | idle.set <myclass, &myclass::idle_cb> (this); |
2608 | |
3579 | |
2609 | io.start (fd, ev::READ); |
3580 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3581 | io.start (); // start it whenever convenient |
|
|
3582 | |
|
|
3583 | io2.start (fd, ev::READ); // set + start in one call |
2610 | } |
3584 | } |
2611 | }; |
3585 | }; |
2612 | |
3586 | |
2613 | |
3587 | |
2614 | =head1 OTHER LANGUAGE BINDINGS |
3588 | =head1 OTHER LANGUAGE BINDINGS |
2615 | |
3589 | |
2616 | Libev does not offer other language bindings itself, but bindings for a |
3590 | Libev does not offer other language bindings itself, but bindings for a |
… | |
… | |
2623 | =item Perl |
3597 | =item Perl |
2624 | |
3598 | |
2625 | The EV module implements the full libev API and is actually used to test |
3599 | The EV module implements the full libev API and is actually used to test |
2626 | libev. EV is developed together with libev. Apart from the EV core module, |
3600 | libev. EV is developed together with libev. Apart from the EV core module, |
2627 | there are additional modules that implement libev-compatible interfaces |
3601 | there are additional modules that implement libev-compatible interfaces |
2628 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3602 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2629 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3603 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3604 | and C<EV::Glib>). |
2630 | |
3605 | |
2631 | It can be found and installed via CPAN, its homepage is found at |
3606 | It can be found and installed via CPAN, its homepage is at |
2632 | L<http://software.schmorp.de/pkg/EV>. |
3607 | L<http://software.schmorp.de/pkg/EV>. |
|
|
3608 | |
|
|
3609 | =item Python |
|
|
3610 | |
|
|
3611 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
3612 | seems to be quite complete and well-documented. |
2633 | |
3613 | |
2634 | =item Ruby |
3614 | =item Ruby |
2635 | |
3615 | |
2636 | Tony Arcieri has written a ruby extension that offers access to a subset |
3616 | Tony Arcieri has written a ruby extension that offers access to a subset |
2637 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3617 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2638 | more on top of it. It can be found via gem servers. Its homepage is at |
3618 | more on top of it. It can be found via gem servers. Its homepage is at |
2639 | L<http://rev.rubyforge.org/>. |
3619 | L<http://rev.rubyforge.org/>. |
2640 | |
3620 | |
|
|
3621 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3622 | makes rev work even on mingw. |
|
|
3623 | |
|
|
3624 | =item Haskell |
|
|
3625 | |
|
|
3626 | A haskell binding to libev is available at |
|
|
3627 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3628 | |
2641 | =item D |
3629 | =item D |
2642 | |
3630 | |
2643 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3631 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2644 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
3632 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3633 | |
|
|
3634 | =item Ocaml |
|
|
3635 | |
|
|
3636 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3637 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3638 | |
|
|
3639 | =item Lua |
|
|
3640 | |
|
|
3641 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3642 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3643 | L<http://github.com/brimworks/lua-ev>. |
2645 | |
3644 | |
2646 | =back |
3645 | =back |
2647 | |
3646 | |
2648 | |
3647 | |
2649 | =head1 MACRO MAGIC |
3648 | =head1 MACRO MAGIC |
… | |
… | |
2661 | |
3660 | |
2662 | This provides the loop I<argument> for functions, if one is required ("ev |
3661 | This provides the loop I<argument> for functions, if one is required ("ev |
2663 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3662 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2664 | C<EV_A_> is used when other arguments are following. Example: |
3663 | C<EV_A_> is used when other arguments are following. Example: |
2665 | |
3664 | |
2666 | ev_unref (EV_A); |
3665 | ev_unref (EV_A); |
2667 | ev_timer_add (EV_A_ watcher); |
3666 | ev_timer_add (EV_A_ watcher); |
2668 | ev_loop (EV_A_ 0); |
3667 | ev_run (EV_A_ 0); |
2669 | |
3668 | |
2670 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3669 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2671 | which is often provided by the following macro. |
3670 | which is often provided by the following macro. |
2672 | |
3671 | |
2673 | =item C<EV_P>, C<EV_P_> |
3672 | =item C<EV_P>, C<EV_P_> |
2674 | |
3673 | |
2675 | This provides the loop I<parameter> for functions, if one is required ("ev |
3674 | This provides the loop I<parameter> for functions, if one is required ("ev |
2676 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
3675 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
2677 | C<EV_P_> is used when other parameters are following. Example: |
3676 | C<EV_P_> is used when other parameters are following. Example: |
2678 | |
3677 | |
2679 | // this is how ev_unref is being declared |
3678 | // this is how ev_unref is being declared |
2680 | static void ev_unref (EV_P); |
3679 | static void ev_unref (EV_P); |
2681 | |
3680 | |
2682 | // this is how you can declare your typical callback |
3681 | // this is how you can declare your typical callback |
2683 | static void cb (EV_P_ ev_timer *w, int revents) |
3682 | static void cb (EV_P_ ev_timer *w, int revents) |
2684 | |
3683 | |
2685 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
3684 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
2686 | suitable for use with C<EV_A>. |
3685 | suitable for use with C<EV_A>. |
2687 | |
3686 | |
2688 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3687 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
… | |
… | |
2704 | |
3703 | |
2705 | Example: Declare and initialise a check watcher, utilising the above |
3704 | Example: Declare and initialise a check watcher, utilising the above |
2706 | macros so it will work regardless of whether multiple loops are supported |
3705 | macros so it will work regardless of whether multiple loops are supported |
2707 | or not. |
3706 | or not. |
2708 | |
3707 | |
2709 | static void |
3708 | static void |
2710 | check_cb (EV_P_ ev_timer *w, int revents) |
3709 | check_cb (EV_P_ ev_timer *w, int revents) |
2711 | { |
3710 | { |
2712 | ev_check_stop (EV_A_ w); |
3711 | ev_check_stop (EV_A_ w); |
2713 | } |
3712 | } |
2714 | |
3713 | |
2715 | ev_check check; |
3714 | ev_check check; |
2716 | ev_check_init (&check, check_cb); |
3715 | ev_check_init (&check, check_cb); |
2717 | ev_check_start (EV_DEFAULT_ &check); |
3716 | ev_check_start (EV_DEFAULT_ &check); |
2718 | ev_loop (EV_DEFAULT_ 0); |
3717 | ev_run (EV_DEFAULT_ 0); |
2719 | |
3718 | |
2720 | =head1 EMBEDDING |
3719 | =head1 EMBEDDING |
2721 | |
3720 | |
2722 | Libev can (and often is) directly embedded into host |
3721 | Libev can (and often is) directly embedded into host |
2723 | applications. Examples of applications that embed it include the Deliantra |
3722 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2737 | =head3 CORE EVENT LOOP |
3736 | =head3 CORE EVENT LOOP |
2738 | |
3737 | |
2739 | To include only the libev core (all the C<ev_*> functions), with manual |
3738 | To include only the libev core (all the C<ev_*> functions), with manual |
2740 | configuration (no autoconf): |
3739 | configuration (no autoconf): |
2741 | |
3740 | |
2742 | #define EV_STANDALONE 1 |
3741 | #define EV_STANDALONE 1 |
2743 | #include "ev.c" |
3742 | #include "ev.c" |
2744 | |
3743 | |
2745 | This will automatically include F<ev.h>, too, and should be done in a |
3744 | This will automatically include F<ev.h>, too, and should be done in a |
2746 | single C source file only to provide the function implementations. To use |
3745 | single C source file only to provide the function implementations. To use |
2747 | it, do the same for F<ev.h> in all files wishing to use this API (best |
3746 | it, do the same for F<ev.h> in all files wishing to use this API (best |
2748 | done by writing a wrapper around F<ev.h> that you can include instead and |
3747 | done by writing a wrapper around F<ev.h> that you can include instead and |
2749 | where you can put other configuration options): |
3748 | where you can put other configuration options): |
2750 | |
3749 | |
2751 | #define EV_STANDALONE 1 |
3750 | #define EV_STANDALONE 1 |
2752 | #include "ev.h" |
3751 | #include "ev.h" |
2753 | |
3752 | |
2754 | Both header files and implementation files can be compiled with a C++ |
3753 | Both header files and implementation files can be compiled with a C++ |
2755 | compiler (at least, thats a stated goal, and breakage will be treated |
3754 | compiler (at least, that's a stated goal, and breakage will be treated |
2756 | as a bug). |
3755 | as a bug). |
2757 | |
3756 | |
2758 | You need the following files in your source tree, or in a directory |
3757 | You need the following files in your source tree, or in a directory |
2759 | in your include path (e.g. in libev/ when using -Ilibev): |
3758 | in your include path (e.g. in libev/ when using -Ilibev): |
2760 | |
3759 | |
2761 | ev.h |
3760 | ev.h |
2762 | ev.c |
3761 | ev.c |
2763 | ev_vars.h |
3762 | ev_vars.h |
2764 | ev_wrap.h |
3763 | ev_wrap.h |
2765 | |
3764 | |
2766 | ev_win32.c required on win32 platforms only |
3765 | ev_win32.c required on win32 platforms only |
2767 | |
3766 | |
2768 | ev_select.c only when select backend is enabled (which is enabled by default) |
3767 | ev_select.c only when select backend is enabled (which is enabled by default) |
2769 | ev_poll.c only when poll backend is enabled (disabled by default) |
3768 | ev_poll.c only when poll backend is enabled (disabled by default) |
2770 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
3769 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2771 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
3770 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2772 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
3771 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2773 | |
3772 | |
2774 | F<ev.c> includes the backend files directly when enabled, so you only need |
3773 | F<ev.c> includes the backend files directly when enabled, so you only need |
2775 | to compile this single file. |
3774 | to compile this single file. |
2776 | |
3775 | |
2777 | =head3 LIBEVENT COMPATIBILITY API |
3776 | =head3 LIBEVENT COMPATIBILITY API |
2778 | |
3777 | |
2779 | To include the libevent compatibility API, also include: |
3778 | To include the libevent compatibility API, also include: |
2780 | |
3779 | |
2781 | #include "event.c" |
3780 | #include "event.c" |
2782 | |
3781 | |
2783 | in the file including F<ev.c>, and: |
3782 | in the file including F<ev.c>, and: |
2784 | |
3783 | |
2785 | #include "event.h" |
3784 | #include "event.h" |
2786 | |
3785 | |
2787 | in the files that want to use the libevent API. This also includes F<ev.h>. |
3786 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2788 | |
3787 | |
2789 | You need the following additional files for this: |
3788 | You need the following additional files for this: |
2790 | |
3789 | |
2791 | event.h |
3790 | event.h |
2792 | event.c |
3791 | event.c |
2793 | |
3792 | |
2794 | =head3 AUTOCONF SUPPORT |
3793 | =head3 AUTOCONF SUPPORT |
2795 | |
3794 | |
2796 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
3795 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2797 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
3796 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2798 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
3797 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2799 | include F<config.h> and configure itself accordingly. |
3798 | include F<config.h> and configure itself accordingly. |
2800 | |
3799 | |
2801 | For this of course you need the m4 file: |
3800 | For this of course you need the m4 file: |
2802 | |
3801 | |
2803 | libev.m4 |
3802 | libev.m4 |
2804 | |
3803 | |
2805 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3804 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2806 | |
3805 | |
2807 | Libev can be configured via a variety of preprocessor symbols you have to |
3806 | Libev can be configured via a variety of preprocessor symbols you have to |
2808 | define before including any of its files. The default in the absence of |
3807 | define before including (or compiling) any of its files. The default in |
2809 | autoconf is noted for every option. |
3808 | the absence of autoconf is documented for every option. |
|
|
3809 | |
|
|
3810 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3811 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3812 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3813 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3814 | users of libev and the libev code itself must be compiled with compatible |
|
|
3815 | settings. |
2810 | |
3816 | |
2811 | =over 4 |
3817 | =over 4 |
2812 | |
3818 | |
|
|
3819 | =item EV_COMPAT3 (h) |
|
|
3820 | |
|
|
3821 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3822 | release of libev comes with wrappers for the functions and symbols that |
|
|
3823 | have been renamed between libev version 3 and 4. |
|
|
3824 | |
|
|
3825 | You can disable these wrappers (to test compatibility with future |
|
|
3826 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3827 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3828 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3829 | typedef in that case. |
|
|
3830 | |
|
|
3831 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3832 | and in some even more future version the compatibility code will be |
|
|
3833 | removed completely. |
|
|
3834 | |
2813 | =item EV_STANDALONE |
3835 | =item EV_STANDALONE (h) |
2814 | |
3836 | |
2815 | Must always be C<1> if you do not use autoconf configuration, which |
3837 | Must always be C<1> if you do not use autoconf configuration, which |
2816 | keeps libev from including F<config.h>, and it also defines dummy |
3838 | keeps libev from including F<config.h>, and it also defines dummy |
2817 | implementations for some libevent functions (such as logging, which is not |
3839 | implementations for some libevent functions (such as logging, which is not |
2818 | supported). It will also not define any of the structs usually found in |
3840 | supported). It will also not define any of the structs usually found in |
2819 | F<event.h> that are not directly supported by the libev core alone. |
3841 | F<event.h> that are not directly supported by the libev core alone. |
2820 | |
3842 | |
|
|
3843 | In standalone mode, libev will still try to automatically deduce the |
|
|
3844 | configuration, but has to be more conservative. |
|
|
3845 | |
2821 | =item EV_USE_MONOTONIC |
3846 | =item EV_USE_MONOTONIC |
2822 | |
3847 | |
2823 | If defined to be C<1>, libev will try to detect the availability of the |
3848 | If defined to be C<1>, libev will try to detect the availability of the |
2824 | monotonic clock option at both compile time and runtime. Otherwise no use |
3849 | monotonic clock option at both compile time and runtime. Otherwise no |
2825 | of the monotonic clock option will be attempted. If you enable this, you |
3850 | use of the monotonic clock option will be attempted. If you enable this, |
2826 | usually have to link against librt or something similar. Enabling it when |
3851 | you usually have to link against librt or something similar. Enabling it |
2827 | the functionality isn't available is safe, though, although you have |
3852 | when the functionality isn't available is safe, though, although you have |
2828 | to make sure you link against any libraries where the C<clock_gettime> |
3853 | to make sure you link against any libraries where the C<clock_gettime> |
2829 | function is hiding in (often F<-lrt>). |
3854 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2830 | |
3855 | |
2831 | =item EV_USE_REALTIME |
3856 | =item EV_USE_REALTIME |
2832 | |
3857 | |
2833 | If defined to be C<1>, libev will try to detect the availability of the |
3858 | If defined to be C<1>, libev will try to detect the availability of the |
2834 | real-time clock option at compile time (and assume its availability at |
3859 | real-time clock option at compile time (and assume its availability |
2835 | runtime if successful). Otherwise no use of the real-time clock option will |
3860 | at runtime if successful). Otherwise no use of the real-time clock |
2836 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3861 | option will be attempted. This effectively replaces C<gettimeofday> |
2837 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3862 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2838 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3863 | correctness. See the note about libraries in the description of |
|
|
3864 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3865 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3866 | |
|
|
3867 | =item EV_USE_CLOCK_SYSCALL |
|
|
3868 | |
|
|
3869 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3870 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3871 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3872 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3873 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3874 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3875 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3876 | higher, as it simplifies linking (no need for C<-lrt>). |
2839 | |
3877 | |
2840 | =item EV_USE_NANOSLEEP |
3878 | =item EV_USE_NANOSLEEP |
2841 | |
3879 | |
2842 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3880 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2843 | and will use it for delays. Otherwise it will use C<select ()>. |
3881 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2859 | |
3897 | |
2860 | =item EV_SELECT_USE_FD_SET |
3898 | =item EV_SELECT_USE_FD_SET |
2861 | |
3899 | |
2862 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3900 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2863 | structure. This is useful if libev doesn't compile due to a missing |
3901 | structure. This is useful if libev doesn't compile due to a missing |
2864 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3902 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2865 | exotic systems. This usually limits the range of file descriptors to some |
3903 | on exotic systems. This usually limits the range of file descriptors to |
2866 | low limit such as 1024 or might have other limitations (winsocket only |
3904 | some low limit such as 1024 or might have other limitations (winsocket |
2867 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3905 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2868 | influence the size of the C<fd_set> used. |
3906 | configures the maximum size of the C<fd_set>. |
2869 | |
3907 | |
2870 | =item EV_SELECT_IS_WINSOCKET |
3908 | =item EV_SELECT_IS_WINSOCKET |
2871 | |
3909 | |
2872 | When defined to C<1>, the select backend will assume that |
3910 | When defined to C<1>, the select backend will assume that |
2873 | select/socket/connect etc. don't understand file descriptors but |
3911 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2875 | be used is the winsock select). This means that it will call |
3913 | be used is the winsock select). This means that it will call |
2876 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3914 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2877 | it is assumed that all these functions actually work on fds, even |
3915 | it is assumed that all these functions actually work on fds, even |
2878 | on win32. Should not be defined on non-win32 platforms. |
3916 | on win32. Should not be defined on non-win32 platforms. |
2879 | |
3917 | |
2880 | =item EV_FD_TO_WIN32_HANDLE |
3918 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2881 | |
3919 | |
2882 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3920 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2883 | file descriptors to socket handles. When not defining this symbol (the |
3921 | file descriptors to socket handles. When not defining this symbol (the |
2884 | default), then libev will call C<_get_osfhandle>, which is usually |
3922 | default), then libev will call C<_get_osfhandle>, which is usually |
2885 | correct. In some cases, programs use their own file descriptor management, |
3923 | correct. In some cases, programs use their own file descriptor management, |
2886 | in which case they can provide this function to map fds to socket handles. |
3924 | in which case they can provide this function to map fds to socket handles. |
|
|
3925 | |
|
|
3926 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3927 | |
|
|
3928 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3929 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3930 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3931 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3932 | |
|
|
3933 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3934 | |
|
|
3935 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3936 | macro can be used to override the C<close> function, useful to unregister |
|
|
3937 | file descriptors again. Note that the replacement function has to close |
|
|
3938 | the underlying OS handle. |
2887 | |
3939 | |
2888 | =item EV_USE_POLL |
3940 | =item EV_USE_POLL |
2889 | |
3941 | |
2890 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3942 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2891 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3943 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
2938 | as well as for signal and thread safety in C<ev_async> watchers. |
3990 | as well as for signal and thread safety in C<ev_async> watchers. |
2939 | |
3991 | |
2940 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3992 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2941 | (from F<signal.h>), which is usually good enough on most platforms. |
3993 | (from F<signal.h>), which is usually good enough on most platforms. |
2942 | |
3994 | |
2943 | =item EV_H |
3995 | =item EV_H (h) |
2944 | |
3996 | |
2945 | The name of the F<ev.h> header file used to include it. The default if |
3997 | The name of the F<ev.h> header file used to include it. The default if |
2946 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3998 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2947 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3999 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2948 | |
4000 | |
2949 | =item EV_CONFIG_H |
4001 | =item EV_CONFIG_H (h) |
2950 | |
4002 | |
2951 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4003 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2952 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4004 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2953 | C<EV_H>, above. |
4005 | C<EV_H>, above. |
2954 | |
4006 | |
2955 | =item EV_EVENT_H |
4007 | =item EV_EVENT_H (h) |
2956 | |
4008 | |
2957 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4009 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2958 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4010 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2959 | |
4011 | |
2960 | =item EV_PROTOTYPES |
4012 | =item EV_PROTOTYPES (h) |
2961 | |
4013 | |
2962 | If defined to be C<0>, then F<ev.h> will not define any function |
4014 | If defined to be C<0>, then F<ev.h> will not define any function |
2963 | prototypes, but still define all the structs and other symbols. This is |
4015 | prototypes, but still define all the structs and other symbols. This is |
2964 | occasionally useful if you want to provide your own wrapper functions |
4016 | occasionally useful if you want to provide your own wrapper functions |
2965 | around libev functions. |
4017 | around libev functions. |
… | |
… | |
2984 | When doing priority-based operations, libev usually has to linearly search |
4036 | When doing priority-based operations, libev usually has to linearly search |
2985 | all the priorities, so having many of them (hundreds) uses a lot of space |
4037 | all the priorities, so having many of them (hundreds) uses a lot of space |
2986 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
4038 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2987 | fine. |
4039 | fine. |
2988 | |
4040 | |
2989 | If your embedding application does not need any priorities, defining these both to |
4041 | If your embedding application does not need any priorities, defining these |
2990 | C<0> will save some memory and CPU. |
4042 | both to C<0> will save some memory and CPU. |
2991 | |
4043 | |
2992 | =item EV_PERIODIC_ENABLE |
4044 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4045 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4046 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
2993 | |
4047 | |
2994 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4048 | If undefined or defined to be C<1> (and the platform supports it), then |
2995 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4049 | the respective watcher type is supported. If defined to be C<0>, then it |
2996 | code. |
4050 | is not. Disabling watcher types mainly saves code size. |
2997 | |
4051 | |
2998 | =item EV_IDLE_ENABLE |
4052 | =item EV_FEATURES |
2999 | |
|
|
3000 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3001 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3002 | code. |
|
|
3003 | |
|
|
3004 | =item EV_EMBED_ENABLE |
|
|
3005 | |
|
|
3006 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3007 | defined to be C<0>, then they are not. |
|
|
3008 | |
|
|
3009 | =item EV_STAT_ENABLE |
|
|
3010 | |
|
|
3011 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3012 | defined to be C<0>, then they are not. |
|
|
3013 | |
|
|
3014 | =item EV_FORK_ENABLE |
|
|
3015 | |
|
|
3016 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3017 | defined to be C<0>, then they are not. |
|
|
3018 | |
|
|
3019 | =item EV_ASYNC_ENABLE |
|
|
3020 | |
|
|
3021 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3022 | defined to be C<0>, then they are not. |
|
|
3023 | |
|
|
3024 | =item EV_MINIMAL |
|
|
3025 | |
4053 | |
3026 | If you need to shave off some kilobytes of code at the expense of some |
4054 | If you need to shave off some kilobytes of code at the expense of some |
3027 | speed, define this symbol to C<1>. Currently this is used to override some |
4055 | speed (but with the full API), you can define this symbol to request |
3028 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4056 | certain subsets of functionality. The default is to enable all features |
3029 | much smaller 2-heap for timer management over the default 4-heap. |
4057 | that can be enabled on the platform. |
|
|
4058 | |
|
|
4059 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4060 | with some broad features you want) and then selectively re-enable |
|
|
4061 | additional parts you want, for example if you want everything minimal, |
|
|
4062 | but multiple event loop support, async and child watchers and the poll |
|
|
4063 | backend, use this: |
|
|
4064 | |
|
|
4065 | #define EV_FEATURES 0 |
|
|
4066 | #define EV_MULTIPLICITY 1 |
|
|
4067 | #define EV_USE_POLL 1 |
|
|
4068 | #define EV_CHILD_ENABLE 1 |
|
|
4069 | #define EV_ASYNC_ENABLE 1 |
|
|
4070 | |
|
|
4071 | The actual value is a bitset, it can be a combination of the following |
|
|
4072 | values: |
|
|
4073 | |
|
|
4074 | =over 4 |
|
|
4075 | |
|
|
4076 | =item C<1> - faster/larger code |
|
|
4077 | |
|
|
4078 | Use larger code to speed up some operations. |
|
|
4079 | |
|
|
4080 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4081 | code size by roughly 30% on amd64). |
|
|
4082 | |
|
|
4083 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4084 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4085 | assertions. |
|
|
4086 | |
|
|
4087 | =item C<2> - faster/larger data structures |
|
|
4088 | |
|
|
4089 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4090 | hash table sizes and so on. This will usually further increase code size |
|
|
4091 | and can additionally have an effect on the size of data structures at |
|
|
4092 | runtime. |
|
|
4093 | |
|
|
4094 | =item C<4> - full API configuration |
|
|
4095 | |
|
|
4096 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4097 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4098 | |
|
|
4099 | =item C<8> - full API |
|
|
4100 | |
|
|
4101 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4102 | details on which parts of the API are still available without this |
|
|
4103 | feature, and do not complain if this subset changes over time. |
|
|
4104 | |
|
|
4105 | =item C<16> - enable all optional watcher types |
|
|
4106 | |
|
|
4107 | Enables all optional watcher types. If you want to selectively enable |
|
|
4108 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4109 | embed, async, child...) you can enable them manually by defining |
|
|
4110 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4111 | |
|
|
4112 | =item C<32> - enable all backends |
|
|
4113 | |
|
|
4114 | This enables all backends - without this feature, you need to enable at |
|
|
4115 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4116 | |
|
|
4117 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4118 | |
|
|
4119 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4120 | default. |
|
|
4121 | |
|
|
4122 | =back |
|
|
4123 | |
|
|
4124 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4125 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4126 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4127 | watchers, timers and monotonic clock support. |
|
|
4128 | |
|
|
4129 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4130 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4131 | your program might be left out as well - a binary starting a timer and an |
|
|
4132 | I/O watcher then might come out at only 5Kb. |
|
|
4133 | |
|
|
4134 | =item EV_AVOID_STDIO |
|
|
4135 | |
|
|
4136 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4137 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4138 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4139 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4140 | big. |
|
|
4141 | |
|
|
4142 | Note that error messages might become less precise when this option is |
|
|
4143 | enabled. |
|
|
4144 | |
|
|
4145 | =item EV_NSIG |
|
|
4146 | |
|
|
4147 | The highest supported signal number, +1 (or, the number of |
|
|
4148 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4149 | automatically, but sometimes this fails, in which case it can be |
|
|
4150 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4151 | good for about any system in existence) can save some memory, as libev |
|
|
4152 | statically allocates some 12-24 bytes per signal number. |
3030 | |
4153 | |
3031 | =item EV_PID_HASHSIZE |
4154 | =item EV_PID_HASHSIZE |
3032 | |
4155 | |
3033 | C<ev_child> watchers use a small hash table to distribute workload by |
4156 | C<ev_child> watchers use a small hash table to distribute workload by |
3034 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4157 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3035 | than enough. If you need to manage thousands of children you might want to |
4158 | usually more than enough. If you need to manage thousands of children you |
3036 | increase this value (I<must> be a power of two). |
4159 | might want to increase this value (I<must> be a power of two). |
3037 | |
4160 | |
3038 | =item EV_INOTIFY_HASHSIZE |
4161 | =item EV_INOTIFY_HASHSIZE |
3039 | |
4162 | |
3040 | C<ev_stat> watchers use a small hash table to distribute workload by |
4163 | C<ev_stat> watchers use a small hash table to distribute workload by |
3041 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4164 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3042 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4165 | disabled), usually more than enough. If you need to manage thousands of |
3043 | watchers you might want to increase this value (I<must> be a power of |
4166 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3044 | two). |
4167 | power of two). |
3045 | |
4168 | |
3046 | =item EV_USE_4HEAP |
4169 | =item EV_USE_4HEAP |
3047 | |
4170 | |
3048 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4171 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3049 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4172 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3050 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4173 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3051 | noticeably faster performance with many (thousands) of watchers. |
4174 | faster performance with many (thousands) of watchers. |
3052 | |
4175 | |
3053 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4176 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3054 | (disabled). |
4177 | will be C<0>. |
3055 | |
4178 | |
3056 | =item EV_HEAP_CACHE_AT |
4179 | =item EV_HEAP_CACHE_AT |
3057 | |
4180 | |
3058 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4181 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3059 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4182 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3060 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4183 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3061 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4184 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3062 | but avoids random read accesses on heap changes. This improves performance |
4185 | but avoids random read accesses on heap changes. This improves performance |
3063 | noticeably with with many (hundreds) of watchers. |
4186 | noticeably with many (hundreds) of watchers. |
3064 | |
4187 | |
3065 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4188 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3066 | (disabled). |
4189 | will be C<0>. |
3067 | |
4190 | |
3068 | =item EV_VERIFY |
4191 | =item EV_VERIFY |
3069 | |
4192 | |
3070 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4193 | Controls how much internal verification (see C<ev_verify ()>) will |
3071 | be done: If set to C<0>, no internal verification code will be compiled |
4194 | be done: If set to C<0>, no internal verification code will be compiled |
3072 | in. If set to C<1>, then verification code will be compiled in, but not |
4195 | in. If set to C<1>, then verification code will be compiled in, but not |
3073 | called. If set to C<2>, then the internal verification code will be |
4196 | called. If set to C<2>, then the internal verification code will be |
3074 | called once per loop, which can slow down libev. If set to C<3>, then the |
4197 | called once per loop, which can slow down libev. If set to C<3>, then the |
3075 | verification code will be called very frequently, which will slow down |
4198 | verification code will be called very frequently, which will slow down |
3076 | libev considerably. |
4199 | libev considerably. |
3077 | |
4200 | |
3078 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4201 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3079 | C<0.> |
4202 | will be C<0>. |
3080 | |
4203 | |
3081 | =item EV_COMMON |
4204 | =item EV_COMMON |
3082 | |
4205 | |
3083 | By default, all watchers have a C<void *data> member. By redefining |
4206 | By default, all watchers have a C<void *data> member. By redefining |
3084 | this macro to a something else you can include more and other types of |
4207 | this macro to something else you can include more and other types of |
3085 | members. You have to define it each time you include one of the files, |
4208 | members. You have to define it each time you include one of the files, |
3086 | though, and it must be identical each time. |
4209 | though, and it must be identical each time. |
3087 | |
4210 | |
3088 | For example, the perl EV module uses something like this: |
4211 | For example, the perl EV module uses something like this: |
3089 | |
4212 | |
3090 | #define EV_COMMON \ |
4213 | #define EV_COMMON \ |
3091 | SV *self; /* contains this struct */ \ |
4214 | SV *self; /* contains this struct */ \ |
3092 | SV *cb_sv, *fh /* note no trailing ";" */ |
4215 | SV *cb_sv, *fh /* note no trailing ";" */ |
3093 | |
4216 | |
3094 | =item EV_CB_DECLARE (type) |
4217 | =item EV_CB_DECLARE (type) |
3095 | |
4218 | |
3096 | =item EV_CB_INVOKE (watcher, revents) |
4219 | =item EV_CB_INVOKE (watcher, revents) |
3097 | |
4220 | |
… | |
… | |
3102 | definition and a statement, respectively. See the F<ev.h> header file for |
4225 | definition and a statement, respectively. See the F<ev.h> header file for |
3103 | their default definitions. One possible use for overriding these is to |
4226 | their default definitions. One possible use for overriding these is to |
3104 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4227 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3105 | method calls instead of plain function calls in C++. |
4228 | method calls instead of plain function calls in C++. |
3106 | |
4229 | |
|
|
4230 | =back |
|
|
4231 | |
3107 | =head2 EXPORTED API SYMBOLS |
4232 | =head2 EXPORTED API SYMBOLS |
3108 | |
4233 | |
3109 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
4234 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3110 | exported symbols, you can use the provided F<Symbol.*> files which list |
4235 | exported symbols, you can use the provided F<Symbol.*> files which list |
3111 | all public symbols, one per line: |
4236 | all public symbols, one per line: |
3112 | |
4237 | |
3113 | Symbols.ev for libev proper |
4238 | Symbols.ev for libev proper |
3114 | Symbols.event for the libevent emulation |
4239 | Symbols.event for the libevent emulation |
3115 | |
4240 | |
3116 | This can also be used to rename all public symbols to avoid clashes with |
4241 | This can also be used to rename all public symbols to avoid clashes with |
3117 | multiple versions of libev linked together (which is obviously bad in |
4242 | multiple versions of libev linked together (which is obviously bad in |
3118 | itself, but sometimes it is inconvenient to avoid this). |
4243 | itself, but sometimes it is inconvenient to avoid this). |
3119 | |
4244 | |
… | |
… | |
3140 | file. |
4265 | file. |
3141 | |
4266 | |
3142 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4267 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3143 | that everybody includes and which overrides some configure choices: |
4268 | that everybody includes and which overrides some configure choices: |
3144 | |
4269 | |
3145 | #define EV_MINIMAL 1 |
4270 | #define EV_FEATURES 8 |
3146 | #define EV_USE_POLL 0 |
4271 | #define EV_USE_SELECT 1 |
3147 | #define EV_MULTIPLICITY 0 |
|
|
3148 | #define EV_PERIODIC_ENABLE 0 |
4272 | #define EV_PREPARE_ENABLE 1 |
|
|
4273 | #define EV_IDLE_ENABLE 1 |
3149 | #define EV_STAT_ENABLE 0 |
4274 | #define EV_SIGNAL_ENABLE 1 |
3150 | #define EV_FORK_ENABLE 0 |
4275 | #define EV_CHILD_ENABLE 1 |
|
|
4276 | #define EV_USE_STDEXCEPT 0 |
3151 | #define EV_CONFIG_H <config.h> |
4277 | #define EV_CONFIG_H <config.h> |
3152 | #define EV_MINPRI 0 |
|
|
3153 | #define EV_MAXPRI 0 |
|
|
3154 | |
4278 | |
3155 | #include "ev++.h" |
4279 | #include "ev++.h" |
3156 | |
4280 | |
3157 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4281 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3158 | |
4282 | |
3159 | #include "ev_cpp.h" |
4283 | #include "ev_cpp.h" |
3160 | #include "ev.c" |
4284 | #include "ev.c" |
3161 | |
4285 | |
|
|
4286 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3162 | |
4287 | |
3163 | =head1 THREADS AND COROUTINES |
4288 | =head2 THREADS AND COROUTINES |
3164 | |
4289 | |
3165 | =head2 THREADS |
4290 | =head3 THREADS |
3166 | |
4291 | |
3167 | Libev itself is completely thread-safe, but it uses no locking. This |
4292 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4293 | documented otherwise, but libev implements no locking itself. This means |
3168 | means that you can use as many loops as you want in parallel, as long as |
4294 | that you can use as many loops as you want in parallel, as long as there |
3169 | only one thread ever calls into one libev function with the same loop |
4295 | are no concurrent calls into any libev function with the same loop |
3170 | parameter. |
4296 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4297 | of course): libev guarantees that different event loops share no data |
|
|
4298 | structures that need any locking. |
3171 | |
4299 | |
3172 | Or put differently: calls with different loop parameters can be done in |
4300 | Or to put it differently: calls with different loop parameters can be done |
3173 | parallel from multiple threads, calls with the same loop parameter must be |
4301 | concurrently from multiple threads, calls with the same loop parameter |
3174 | done serially (but can be done from different threads, as long as only one |
4302 | must be done serially (but can be done from different threads, as long as |
3175 | thread ever is inside a call at any point in time, e.g. by using a mutex |
4303 | only one thread ever is inside a call at any point in time, e.g. by using |
3176 | per loop). |
4304 | a mutex per loop). |
3177 | |
4305 | |
3178 | If you want to know which design is best for your problem, then I cannot |
4306 | Specifically to support threads (and signal handlers), libev implements |
|
|
4307 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4308 | concurrency on the same event loop, namely waking it up "from the |
|
|
4309 | outside". |
|
|
4310 | |
|
|
4311 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4312 | without or something else still) is best for your problem, then I cannot |
3179 | help you but by giving some generic advice: |
4313 | help you, but here is some generic advice: |
3180 | |
4314 | |
3181 | =over 4 |
4315 | =over 4 |
3182 | |
4316 | |
3183 | =item * most applications have a main thread: use the default libev loop |
4317 | =item * most applications have a main thread: use the default libev loop |
3184 | in that thread, or create a separate thread running only the default loop. |
4318 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3196 | |
4330 | |
3197 | Choosing a model is hard - look around, learn, know that usually you can do |
4331 | Choosing a model is hard - look around, learn, know that usually you can do |
3198 | better than you currently do :-) |
4332 | better than you currently do :-) |
3199 | |
4333 | |
3200 | =item * often you need to talk to some other thread which blocks in the |
4334 | =item * often you need to talk to some other thread which blocks in the |
|
|
4335 | event loop. |
|
|
4336 | |
3201 | event loop - C<ev_async> watchers can be used to wake them up from other |
4337 | C<ev_async> watchers can be used to wake them up from other threads safely |
3202 | threads safely (or from signal contexts...). |
4338 | (or from signal contexts...). |
|
|
4339 | |
|
|
4340 | An example use would be to communicate signals or other events that only |
|
|
4341 | work in the default loop by registering the signal watcher with the |
|
|
4342 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
4343 | watcher callback into the event loop interested in the signal. |
3203 | |
4344 | |
3204 | =back |
4345 | =back |
3205 | |
4346 | |
|
|
4347 | =head4 THREAD LOCKING EXAMPLE |
|
|
4348 | |
|
|
4349 | Here is a fictitious example of how to run an event loop in a different |
|
|
4350 | thread than where callbacks are being invoked and watchers are |
|
|
4351 | created/added/removed. |
|
|
4352 | |
|
|
4353 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4354 | which uses exactly this technique (which is suited for many high-level |
|
|
4355 | languages). |
|
|
4356 | |
|
|
4357 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4358 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4359 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4360 | |
|
|
4361 | First, you need to associate some data with the event loop: |
|
|
4362 | |
|
|
4363 | typedef struct { |
|
|
4364 | mutex_t lock; /* global loop lock */ |
|
|
4365 | ev_async async_w; |
|
|
4366 | thread_t tid; |
|
|
4367 | cond_t invoke_cv; |
|
|
4368 | } userdata; |
|
|
4369 | |
|
|
4370 | void prepare_loop (EV_P) |
|
|
4371 | { |
|
|
4372 | // for simplicity, we use a static userdata struct. |
|
|
4373 | static userdata u; |
|
|
4374 | |
|
|
4375 | ev_async_init (&u->async_w, async_cb); |
|
|
4376 | ev_async_start (EV_A_ &u->async_w); |
|
|
4377 | |
|
|
4378 | pthread_mutex_init (&u->lock, 0); |
|
|
4379 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4380 | |
|
|
4381 | // now associate this with the loop |
|
|
4382 | ev_set_userdata (EV_A_ u); |
|
|
4383 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4384 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4385 | |
|
|
4386 | // then create the thread running ev_loop |
|
|
4387 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4388 | } |
|
|
4389 | |
|
|
4390 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4391 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4392 | that might have been added: |
|
|
4393 | |
|
|
4394 | static void |
|
|
4395 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4396 | { |
|
|
4397 | // just used for the side effects |
|
|
4398 | } |
|
|
4399 | |
|
|
4400 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4401 | protecting the loop data, respectively. |
|
|
4402 | |
|
|
4403 | static void |
|
|
4404 | l_release (EV_P) |
|
|
4405 | { |
|
|
4406 | userdata *u = ev_userdata (EV_A); |
|
|
4407 | pthread_mutex_unlock (&u->lock); |
|
|
4408 | } |
|
|
4409 | |
|
|
4410 | static void |
|
|
4411 | l_acquire (EV_P) |
|
|
4412 | { |
|
|
4413 | userdata *u = ev_userdata (EV_A); |
|
|
4414 | pthread_mutex_lock (&u->lock); |
|
|
4415 | } |
|
|
4416 | |
|
|
4417 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4418 | into C<ev_run>: |
|
|
4419 | |
|
|
4420 | void * |
|
|
4421 | l_run (void *thr_arg) |
|
|
4422 | { |
|
|
4423 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4424 | |
|
|
4425 | l_acquire (EV_A); |
|
|
4426 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4427 | ev_run (EV_A_ 0); |
|
|
4428 | l_release (EV_A); |
|
|
4429 | |
|
|
4430 | return 0; |
|
|
4431 | } |
|
|
4432 | |
|
|
4433 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4434 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4435 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4436 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4437 | and b) skipping inter-thread-communication when there are no pending |
|
|
4438 | watchers is very beneficial): |
|
|
4439 | |
|
|
4440 | static void |
|
|
4441 | l_invoke (EV_P) |
|
|
4442 | { |
|
|
4443 | userdata *u = ev_userdata (EV_A); |
|
|
4444 | |
|
|
4445 | while (ev_pending_count (EV_A)) |
|
|
4446 | { |
|
|
4447 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4448 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4449 | } |
|
|
4450 | } |
|
|
4451 | |
|
|
4452 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4453 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4454 | thread to continue: |
|
|
4455 | |
|
|
4456 | static void |
|
|
4457 | real_invoke_pending (EV_P) |
|
|
4458 | { |
|
|
4459 | userdata *u = ev_userdata (EV_A); |
|
|
4460 | |
|
|
4461 | pthread_mutex_lock (&u->lock); |
|
|
4462 | ev_invoke_pending (EV_A); |
|
|
4463 | pthread_cond_signal (&u->invoke_cv); |
|
|
4464 | pthread_mutex_unlock (&u->lock); |
|
|
4465 | } |
|
|
4466 | |
|
|
4467 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4468 | event loop, you will now have to lock: |
|
|
4469 | |
|
|
4470 | ev_timer timeout_watcher; |
|
|
4471 | userdata *u = ev_userdata (EV_A); |
|
|
4472 | |
|
|
4473 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4474 | |
|
|
4475 | pthread_mutex_lock (&u->lock); |
|
|
4476 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4477 | ev_async_send (EV_A_ &u->async_w); |
|
|
4478 | pthread_mutex_unlock (&u->lock); |
|
|
4479 | |
|
|
4480 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4481 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4482 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4483 | watchers in the next event loop iteration. |
|
|
4484 | |
3206 | =head2 COROUTINES |
4485 | =head3 COROUTINES |
3207 | |
4486 | |
3208 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4487 | Libev is very accommodating to coroutines ("cooperative threads"): |
3209 | libev fully supports nesting calls to it's functions from different |
4488 | libev fully supports nesting calls to its functions from different |
3210 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4489 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3211 | different coroutines and switch freely between both coroutines running the |
4490 | different coroutines, and switch freely between both coroutines running |
3212 | loop, as long as you don't confuse yourself). The only exception is that |
4491 | the loop, as long as you don't confuse yourself). The only exception is |
3213 | you must not do this from C<ev_periodic> reschedule callbacks. |
4492 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3214 | |
4493 | |
3215 | Care has been invested into making sure that libev does not keep local |
4494 | Care has been taken to ensure that libev does not keep local state inside |
3216 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4495 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3217 | switches. |
4496 | they do not call any callbacks. |
3218 | |
4497 | |
|
|
4498 | =head2 COMPILER WARNINGS |
3219 | |
4499 | |
3220 | =head1 COMPLEXITIES |
4500 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4501 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4502 | scared by this. |
3221 | |
4503 | |
3222 | In this section the complexities of (many of) the algorithms used inside |
4504 | However, these are unavoidable for many reasons. For one, each compiler |
3223 | libev will be explained. For complexity discussions about backends see the |
4505 | has different warnings, and each user has different tastes regarding |
3224 | documentation for C<ev_default_init>. |
4506 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4507 | targeting a specific compiler and compiler-version. |
3225 | |
4508 | |
3226 | All of the following are about amortised time: If an array needs to be |
4509 | Another reason is that some compiler warnings require elaborate |
3227 | extended, libev needs to realloc and move the whole array, but this |
4510 | workarounds, or other changes to the code that make it less clear and less |
3228 | happens asymptotically never with higher number of elements, so O(1) might |
4511 | maintainable. |
3229 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3230 | it is much faster and asymptotically approaches constant time. |
|
|
3231 | |
4512 | |
3232 | =over 4 |
4513 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4514 | wrong (because they don't actually warn about the condition their message |
|
|
4515 | seems to warn about). For example, certain older gcc versions had some |
|
|
4516 | warnings that resulted in an extreme number of false positives. These have |
|
|
4517 | been fixed, but some people still insist on making code warn-free with |
|
|
4518 | such buggy versions. |
3233 | |
4519 | |
3234 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4520 | While libev is written to generate as few warnings as possible, |
|
|
4521 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4522 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4523 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4524 | warnings, not errors, or proof of bugs. |
3235 | |
4525 | |
3236 | This means that, when you have a watcher that triggers in one hour and |
|
|
3237 | there are 100 watchers that would trigger before that then inserting will |
|
|
3238 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3239 | |
4526 | |
3240 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4527 | =head2 VALGRIND |
3241 | |
4528 | |
3242 | That means that changing a timer costs less than removing/adding them |
4529 | Valgrind has a special section here because it is a popular tool that is |
3243 | as only the relative motion in the event queue has to be paid for. |
4530 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3244 | |
4531 | |
3245 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4532 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4533 | in libev, then check twice: If valgrind reports something like: |
3246 | |
4534 | |
3247 | These just add the watcher into an array or at the head of a list. |
4535 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4536 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4537 | ==2274== still reachable: 256 bytes in 1 blocks. |
3248 | |
4538 | |
3249 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4539 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4540 | is not a memleak - the memory is still being referenced, and didn't leak. |
3250 | |
4541 | |
3251 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4542 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4543 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4544 | although an acceptable workaround has been found here), or it might be |
|
|
4545 | confused. |
3252 | |
4546 | |
3253 | These watchers are stored in lists then need to be walked to find the |
4547 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3254 | correct watcher to remove. The lists are usually short (you don't usually |
4548 | make it into some kind of religion. |
3255 | have many watchers waiting for the same fd or signal). |
|
|
3256 | |
4549 | |
3257 | =item Finding the next timer in each loop iteration: O(1) |
4550 | If you are unsure about something, feel free to contact the mailing list |
|
|
4551 | with the full valgrind report and an explanation on why you think this |
|
|
4552 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4553 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4554 | of learning how to interpret valgrind properly. |
3258 | |
4555 | |
3259 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4556 | If you need, for some reason, empty reports from valgrind for your project |
3260 | fixed position in the storage array. |
4557 | I suggest using suppression lists. |
3261 | |
4558 | |
3262 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3263 | |
4559 | |
3264 | A change means an I/O watcher gets started or stopped, which requires |
4560 | =head1 PORTABILITY NOTES |
3265 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3266 | on backend and whether C<ev_io_set> was used). |
|
|
3267 | |
4561 | |
3268 | =item Activating one watcher (putting it into the pending state): O(1) |
4562 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
3269 | |
4563 | |
3270 | =item Priority handling: O(number_of_priorities) |
4564 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4565 | interfaces but I<disables> them by default. |
3271 | |
4566 | |
3272 | Priorities are implemented by allocating some space for each |
4567 | That means that libev compiled in the default environment doesn't support |
3273 | priority. When doing priority-based operations, libev usually has to |
4568 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
3274 | linearly search all the priorities, but starting/stopping and activating |
|
|
3275 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3276 | |
4569 | |
3277 | =item Sending an ev_async: O(1) |
4570 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4571 | by enabling the large file API, which makes them incompatible with the |
|
|
4572 | standard libev compiled for their system. |
3278 | |
4573 | |
3279 | =item Processing ev_async_send: O(number_of_async_watchers) |
4574 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4575 | suddenly make it incompatible to the default compile time environment, |
|
|
4576 | i.e. all programs not using special compile switches. |
3280 | |
4577 | |
3281 | =item Processing signals: O(max_signal_number) |
4578 | =head2 OS/X AND DARWIN BUGS |
3282 | |
4579 | |
3283 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4580 | The whole thing is a bug if you ask me - basically any system interface |
3284 | calls in the current loop iteration. Checking for async and signal events |
4581 | you touch is broken, whether it is locales, poll, kqueue or even the |
3285 | involves iterating over all running async watchers or all signal numbers. |
4582 | OpenGL drivers. |
3286 | |
4583 | |
3287 | =back |
4584 | =head3 C<kqueue> is buggy |
3288 | |
4585 | |
|
|
4586 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4587 | only sockets, many support pipes. |
3289 | |
4588 | |
3290 | =head1 Win32 platform limitations and workarounds |
4589 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4590 | rotten platform, but of course you can still ask for it when creating a |
|
|
4591 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4592 | probably going to work well. |
|
|
4593 | |
|
|
4594 | =head3 C<poll> is buggy |
|
|
4595 | |
|
|
4596 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4597 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4598 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4599 | |
|
|
4600 | Libev tries to work around this by not using C<poll> by default on |
|
|
4601 | this rotten platform, but of course you can still ask for it when creating |
|
|
4602 | a loop. |
|
|
4603 | |
|
|
4604 | =head3 C<select> is buggy |
|
|
4605 | |
|
|
4606 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4607 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4608 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4609 | you use more. |
|
|
4610 | |
|
|
4611 | There is an undocumented "workaround" for this - defining |
|
|
4612 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4613 | work on OS/X. |
|
|
4614 | |
|
|
4615 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4616 | |
|
|
4617 | =head3 C<errno> reentrancy |
|
|
4618 | |
|
|
4619 | The default compile environment on Solaris is unfortunately so |
|
|
4620 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4621 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4622 | defined by default. A valid, if stupid, implementation choice. |
|
|
4623 | |
|
|
4624 | If you want to use libev in threaded environments you have to make sure |
|
|
4625 | it's compiled with C<_REENTRANT> defined. |
|
|
4626 | |
|
|
4627 | =head3 Event port backend |
|
|
4628 | |
|
|
4629 | The scalable event interface for Solaris is called "event |
|
|
4630 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4631 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4632 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4633 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4634 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4635 | great. |
|
|
4636 | |
|
|
4637 | If you can't get it to work, you can try running the program by setting |
|
|
4638 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4639 | C<select> backends. |
|
|
4640 | |
|
|
4641 | =head2 AIX POLL BUG |
|
|
4642 | |
|
|
4643 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4644 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4645 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4646 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4647 | |
|
|
4648 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4649 | |
|
|
4650 | =head3 General issues |
3291 | |
4651 | |
3292 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4652 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3293 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4653 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3294 | model. Libev still offers limited functionality on this platform in |
4654 | model. Libev still offers limited functionality on this platform in |
3295 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4655 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3296 | descriptors. This only applies when using Win32 natively, not when using |
4656 | descriptors. This only applies when using Win32 natively, not when using |
3297 | e.g. cygwin. |
4657 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4658 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4659 | environment. |
3298 | |
4660 | |
3299 | Lifting these limitations would basically require the full |
4661 | Lifting these limitations would basically require the full |
3300 | re-implementation of the I/O system. If you are into these kinds of |
4662 | re-implementation of the I/O system. If you are into this kind of thing, |
3301 | things, then note that glib does exactly that for you in a very portable |
4663 | then note that glib does exactly that for you in a very portable way (note |
3302 | way (note also that glib is the slowest event library known to man). |
4664 | also that glib is the slowest event library known to man). |
3303 | |
4665 | |
3304 | There is no supported compilation method available on windows except |
4666 | There is no supported compilation method available on windows except |
3305 | embedding it into other applications. |
4667 | embedding it into other applications. |
|
|
4668 | |
|
|
4669 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4670 | tries its best, but under most conditions, signals will simply not work. |
|
|
4671 | |
|
|
4672 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
4673 | accept large writes: instead of resulting in a partial write, windows will |
|
|
4674 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
4675 | so make sure you only write small amounts into your sockets (less than a |
|
|
4676 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
4677 | available). |
3306 | |
4678 | |
3307 | Due to the many, low, and arbitrary limits on the win32 platform and |
4679 | Due to the many, low, and arbitrary limits on the win32 platform and |
3308 | the abysmal performance of winsockets, using a large number of sockets |
4680 | the abysmal performance of winsockets, using a large number of sockets |
3309 | is not recommended (and not reasonable). If your program needs to use |
4681 | is not recommended (and not reasonable). If your program needs to use |
3310 | more than a hundred or so sockets, then likely it needs to use a totally |
4682 | more than a hundred or so sockets, then likely it needs to use a totally |
3311 | different implementation for windows, as libev offers the POSIX readiness |
4683 | different implementation for windows, as libev offers the POSIX readiness |
3312 | notification model, which cannot be implemented efficiently on windows |
4684 | notification model, which cannot be implemented efficiently on windows |
3313 | (Microsoft monopoly games). |
4685 | (due to Microsoft monopoly games). |
3314 | |
4686 | |
3315 | =over 4 |
4687 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
4688 | section for details) and use the following F<evwrap.h> header file instead |
|
|
4689 | of F<ev.h>: |
3316 | |
4690 | |
|
|
4691 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
4692 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
4693 | |
|
|
4694 | #include "ev.h" |
|
|
4695 | |
|
|
4696 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
4697 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
4698 | |
|
|
4699 | #include "evwrap.h" |
|
|
4700 | #include "ev.c" |
|
|
4701 | |
3317 | =item The winsocket select function |
4702 | =head3 The winsocket C<select> function |
3318 | |
4703 | |
3319 | The winsocket C<select> function doesn't follow POSIX in that it |
4704 | The winsocket C<select> function doesn't follow POSIX in that it |
3320 | requires socket I<handles> and not socket I<file descriptors> (it is |
4705 | requires socket I<handles> and not socket I<file descriptors> (it is |
3321 | also extremely buggy). This makes select very inefficient, and also |
4706 | also extremely buggy). This makes select very inefficient, and also |
3322 | requires a mapping from file descriptors to socket handles. See the |
4707 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
4708 | C runtime provides the function C<_open_osfhandle> for this). See the |
3323 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
4709 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
3324 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
4710 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
3325 | |
4711 | |
3326 | The configuration for a "naked" win32 using the Microsoft runtime |
4712 | The configuration for a "naked" win32 using the Microsoft runtime |
3327 | libraries and raw winsocket select is: |
4713 | libraries and raw winsocket select is: |
3328 | |
4714 | |
3329 | #define EV_USE_SELECT 1 |
4715 | #define EV_USE_SELECT 1 |
3330 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4716 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3331 | |
4717 | |
3332 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4718 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3333 | complexity in the O(n²) range when using win32. |
4719 | complexity in the O(n²) range when using win32. |
3334 | |
4720 | |
3335 | =item Limited number of file descriptors |
4721 | =head3 Limited number of file descriptors |
3336 | |
4722 | |
3337 | Windows has numerous arbitrary (and low) limits on things. |
4723 | Windows has numerous arbitrary (and low) limits on things. |
3338 | |
4724 | |
3339 | Early versions of winsocket's select only supported waiting for a maximum |
4725 | Early versions of winsocket's select only supported waiting for a maximum |
3340 | of C<64> handles (probably owning to the fact that all windows kernels |
4726 | of C<64> handles (probably owning to the fact that all windows kernels |
3341 | can only wait for C<64> things at the same time internally; Microsoft |
4727 | can only wait for C<64> things at the same time internally; Microsoft |
3342 | recommends spawning a chain of threads and wait for 63 handles and the |
4728 | recommends spawning a chain of threads and wait for 63 handles and the |
3343 | previous thread in each. Great). |
4729 | previous thread in each. Sounds great!). |
3344 | |
4730 | |
3345 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4731 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3346 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4732 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3347 | call (which might be in libev or elsewhere, for example, perl does its own |
4733 | call (which might be in libev or elsewhere, for example, perl and many |
3348 | select emulation on windows). |
4734 | other interpreters do their own select emulation on windows). |
3349 | |
4735 | |
3350 | Another limit is the number of file descriptors in the Microsoft runtime |
4736 | Another limit is the number of file descriptors in the Microsoft runtime |
3351 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4737 | libraries, which by default is C<64> (there must be a hidden I<64> |
3352 | or something like this inside Microsoft). You can increase this by calling |
4738 | fetish or something like this inside Microsoft). You can increase this |
3353 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4739 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3354 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4740 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3355 | libraries. |
|
|
3356 | |
|
|
3357 | This might get you to about C<512> or C<2048> sockets (depending on |
4741 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3358 | windows version and/or the phase of the moon). To get more, you need to |
4742 | (depending on windows version and/or the phase of the moon). To get more, |
3359 | wrap all I/O functions and provide your own fd management, but the cost of |
4743 | you need to wrap all I/O functions and provide your own fd management, but |
3360 | calling select (O(n²)) will likely make this unworkable. |
4744 | the cost of calling select (O(n²)) will likely make this unworkable. |
3361 | |
4745 | |
3362 | =back |
|
|
3363 | |
|
|
3364 | |
|
|
3365 | =head1 PORTABILITY REQUIREMENTS |
4746 | =head2 PORTABILITY REQUIREMENTS |
3366 | |
4747 | |
3367 | In addition to a working ISO-C implementation, libev relies on a few |
4748 | In addition to a working ISO-C implementation and of course the |
3368 | additional extensions: |
4749 | backend-specific APIs, libev relies on a few additional extensions: |
3369 | |
4750 | |
3370 | =over 4 |
4751 | =over 4 |
3371 | |
4752 | |
|
|
4753 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
4754 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
4755 | |
|
|
4756 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4757 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
4758 | assumes that the same (machine) code can be used to call any watcher |
|
|
4759 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4760 | calls them using an C<ev_watcher *> internally. |
|
|
4761 | |
3372 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4762 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3373 | |
4763 | |
3374 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4764 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3375 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4765 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3376 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4766 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3377 | believed to be sufficiently portable. |
4767 | believed to be sufficiently portable. |
3378 | |
4768 | |
3379 | =item C<sigprocmask> must work in a threaded environment |
4769 | =item C<sigprocmask> must work in a threaded environment |
3380 | |
4770 | |
… | |
… | |
3389 | except the initial one, and run the default loop in the initial thread as |
4779 | except the initial one, and run the default loop in the initial thread as |
3390 | well. |
4780 | well. |
3391 | |
4781 | |
3392 | =item C<long> must be large enough for common memory allocation sizes |
4782 | =item C<long> must be large enough for common memory allocation sizes |
3393 | |
4783 | |
3394 | To improve portability and simplify using libev, libev uses C<long> |
4784 | To improve portability and simplify its API, libev uses C<long> internally |
3395 | internally instead of C<size_t> when allocating its data structures. On |
4785 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3396 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4786 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3397 | is still at least 31 bits everywhere, which is enough for hundreds of |
4787 | least 31 bits everywhere, which is enough for hundreds of millions of |
3398 | millions of watchers. |
4788 | watchers. |
3399 | |
4789 | |
3400 | =item C<double> must hold a time value in seconds with enough accuracy |
4790 | =item C<double> must hold a time value in seconds with enough accuracy |
3401 | |
4791 | |
3402 | The type C<double> is used to represent timestamps. It is required to |
4792 | The type C<double> is used to represent timestamps. It is required to |
3403 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4793 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3404 | enough for at least into the year 4000. This requirement is fulfilled by |
4794 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4795 | (the design goal for libev). This requirement is overfulfilled by |
3405 | implementations implementing IEEE 754 (basically all existing ones). |
4796 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4797 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3406 | |
4798 | |
3407 | =back |
4799 | =back |
3408 | |
4800 | |
3409 | If you know of other additional requirements drop me a note. |
4801 | If you know of other additional requirements drop me a note. |
3410 | |
4802 | |
3411 | |
4803 | |
3412 | =head1 COMPILER WARNINGS |
4804 | =head1 ALGORITHMIC COMPLEXITIES |
3413 | |
4805 | |
3414 | Depending on your compiler and compiler settings, you might get no or a |
4806 | In this section the complexities of (many of) the algorithms used inside |
3415 | lot of warnings when compiling libev code. Some people are apparently |
4807 | libev will be documented. For complexity discussions about backends see |
3416 | scared by this. |
4808 | the documentation for C<ev_default_init>. |
3417 | |
4809 | |
3418 | However, these are unavoidable for many reasons. For one, each compiler |
4810 | All of the following are about amortised time: If an array needs to be |
3419 | has different warnings, and each user has different tastes regarding |
4811 | extended, libev needs to realloc and move the whole array, but this |
3420 | warning options. "Warn-free" code therefore cannot be a goal except when |
4812 | happens asymptotically rarer with higher number of elements, so O(1) might |
3421 | targeting a specific compiler and compiler-version. |
4813 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4814 | average it is much faster and asymptotically approaches constant time. |
3422 | |
4815 | |
3423 | Another reason is that some compiler warnings require elaborate |
4816 | =over 4 |
3424 | workarounds, or other changes to the code that make it less clear and less |
|
|
3425 | maintainable. |
|
|
3426 | |
4817 | |
3427 | And of course, some compiler warnings are just plain stupid, or simply |
4818 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3428 | wrong (because they don't actually warn about the condition their message |
|
|
3429 | seems to warn about). |
|
|
3430 | |
4819 | |
3431 | While libev is written to generate as few warnings as possible, |
4820 | This means that, when you have a watcher that triggers in one hour and |
3432 | "warn-free" code is not a goal, and it is recommended not to build libev |
4821 | there are 100 watchers that would trigger before that, then inserting will |
3433 | with any compiler warnings enabled unless you are prepared to cope with |
4822 | have to skip roughly seven (C<ld 100>) of these watchers. |
3434 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3435 | warnings, not errors, or proof of bugs. |
|
|
3436 | |
4823 | |
|
|
4824 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3437 | |
4825 | |
3438 | =head1 VALGRIND |
4826 | That means that changing a timer costs less than removing/adding them, |
|
|
4827 | as only the relative motion in the event queue has to be paid for. |
3439 | |
4828 | |
3440 | Valgrind has a special section here because it is a popular tool that is |
4829 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3441 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3442 | |
4830 | |
3443 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4831 | These just add the watcher into an array or at the head of a list. |
3444 | in libev, then check twice: If valgrind reports something like: |
|
|
3445 | |
4832 | |
3446 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4833 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3447 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3448 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3449 | |
4834 | |
3450 | Then there is no memory leak. Similarly, under some circumstances, |
4835 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3451 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3452 | might be confused (it is a very good tool, but only a tool). |
|
|
3453 | |
4836 | |
3454 | If you are unsure about something, feel free to contact the mailing list |
4837 | These watchers are stored in lists, so they need to be walked to find the |
3455 | with the full valgrind report and an explanation on why you think this is |
4838 | correct watcher to remove. The lists are usually short (you don't usually |
3456 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4839 | have many watchers waiting for the same fd or signal: one is typical, two |
3457 | no bug" answer and take the chance of learning how to interpret valgrind |
4840 | is rare). |
3458 | properly. |
|
|
3459 | |
4841 | |
3460 | If you need, for some reason, empty reports from valgrind for your project |
4842 | =item Finding the next timer in each loop iteration: O(1) |
3461 | I suggest using suppression lists. |
|
|
3462 | |
4843 | |
|
|
4844 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4845 | fixed position in the storage array. |
|
|
4846 | |
|
|
4847 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4848 | |
|
|
4849 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4850 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4851 | on backend and whether C<ev_io_set> was used). |
|
|
4852 | |
|
|
4853 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4854 | |
|
|
4855 | =item Priority handling: O(number_of_priorities) |
|
|
4856 | |
|
|
4857 | Priorities are implemented by allocating some space for each |
|
|
4858 | priority. When doing priority-based operations, libev usually has to |
|
|
4859 | linearly search all the priorities, but starting/stopping and activating |
|
|
4860 | watchers becomes O(1) with respect to priority handling. |
|
|
4861 | |
|
|
4862 | =item Sending an ev_async: O(1) |
|
|
4863 | |
|
|
4864 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4865 | |
|
|
4866 | =item Processing signals: O(max_signal_number) |
|
|
4867 | |
|
|
4868 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4869 | calls in the current loop iteration. Checking for async and signal events |
|
|
4870 | involves iterating over all running async watchers or all signal numbers. |
|
|
4871 | |
|
|
4872 | =back |
|
|
4873 | |
|
|
4874 | |
|
|
4875 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4876 | |
|
|
4877 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4878 | |
|
|
4879 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4880 | compatibility, so most programs should still compile. Those might be |
|
|
4881 | removed in later versions of libev, so better update early than late. |
|
|
4882 | |
|
|
4883 | =over 4 |
|
|
4884 | |
|
|
4885 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
4886 | |
|
|
4887 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
4888 | |
|
|
4889 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
4890 | ev_loop_fork (EV_DEFAULT); |
|
|
4891 | |
|
|
4892 | =item function/symbol renames |
|
|
4893 | |
|
|
4894 | A number of functions and symbols have been renamed: |
|
|
4895 | |
|
|
4896 | ev_loop => ev_run |
|
|
4897 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
4898 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
4899 | |
|
|
4900 | ev_unloop => ev_break |
|
|
4901 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
4902 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
4903 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
4904 | |
|
|
4905 | EV_TIMEOUT => EV_TIMER |
|
|
4906 | |
|
|
4907 | ev_loop_count => ev_iteration |
|
|
4908 | ev_loop_depth => ev_depth |
|
|
4909 | ev_loop_verify => ev_verify |
|
|
4910 | |
|
|
4911 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4912 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
4913 | associated constants have been renamed to not collide with the C<struct |
|
|
4914 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
4915 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
4916 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
4917 | typedef. |
|
|
4918 | |
|
|
4919 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4920 | |
|
|
4921 | The backward compatibility mechanism can be controlled by |
|
|
4922 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4923 | section. |
|
|
4924 | |
|
|
4925 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4926 | |
|
|
4927 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4928 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4929 | and work, but the library code will of course be larger. |
|
|
4930 | |
|
|
4931 | =back |
|
|
4932 | |
|
|
4933 | |
|
|
4934 | =head1 GLOSSARY |
|
|
4935 | |
|
|
4936 | =over 4 |
|
|
4937 | |
|
|
4938 | =item active |
|
|
4939 | |
|
|
4940 | A watcher is active as long as it has been started and not yet stopped. |
|
|
4941 | See L<WATCHER STATES> for details. |
|
|
4942 | |
|
|
4943 | =item application |
|
|
4944 | |
|
|
4945 | In this document, an application is whatever is using libev. |
|
|
4946 | |
|
|
4947 | =item backend |
|
|
4948 | |
|
|
4949 | The part of the code dealing with the operating system interfaces. |
|
|
4950 | |
|
|
4951 | =item callback |
|
|
4952 | |
|
|
4953 | The address of a function that is called when some event has been |
|
|
4954 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4955 | received the event, and the actual event bitset. |
|
|
4956 | |
|
|
4957 | =item callback/watcher invocation |
|
|
4958 | |
|
|
4959 | The act of calling the callback associated with a watcher. |
|
|
4960 | |
|
|
4961 | =item event |
|
|
4962 | |
|
|
4963 | A change of state of some external event, such as data now being available |
|
|
4964 | for reading on a file descriptor, time having passed or simply not having |
|
|
4965 | any other events happening anymore. |
|
|
4966 | |
|
|
4967 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4968 | C<EV_TIMER>). |
|
|
4969 | |
|
|
4970 | =item event library |
|
|
4971 | |
|
|
4972 | A software package implementing an event model and loop. |
|
|
4973 | |
|
|
4974 | =item event loop |
|
|
4975 | |
|
|
4976 | An entity that handles and processes external events and converts them |
|
|
4977 | into callback invocations. |
|
|
4978 | |
|
|
4979 | =item event model |
|
|
4980 | |
|
|
4981 | The model used to describe how an event loop handles and processes |
|
|
4982 | watchers and events. |
|
|
4983 | |
|
|
4984 | =item pending |
|
|
4985 | |
|
|
4986 | A watcher is pending as soon as the corresponding event has been |
|
|
4987 | detected. See L<WATCHER STATES> for details. |
|
|
4988 | |
|
|
4989 | =item real time |
|
|
4990 | |
|
|
4991 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4992 | |
|
|
4993 | =item wall-clock time |
|
|
4994 | |
|
|
4995 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4996 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4997 | clock. |
|
|
4998 | |
|
|
4999 | =item watcher |
|
|
5000 | |
|
|
5001 | A data structure that describes interest in certain events. Watchers need |
|
|
5002 | to be started (attached to an event loop) before they can receive events. |
|
|
5003 | |
|
|
5004 | =back |
3463 | |
5005 | |
3464 | =head1 AUTHOR |
5006 | =head1 AUTHOR |
3465 | |
5007 | |
3466 | Marc Lehmann <libev@schmorp.de>. |
5008 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3467 | |
5009 | |