… | |
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8 | |
8 | |
9 | =head1 DESCRIPTION |
9 | =head1 DESCRIPTION |
10 | |
10 | |
11 | Libev is an event loop: you register interest in certain events (such as a |
11 | Libev is an event loop: you register interest in certain events (such as a |
12 | file descriptor being readable or a timeout occuring), and it will manage |
12 | file descriptor being readable or a timeout occuring), and it will manage |
13 | these event sources and provide your program events. |
13 | these event sources and provide your program with events. |
14 | |
14 | |
15 | To do this, it must take more or less complete control over your process |
15 | To do this, it must take more or less complete control over your process |
16 | (or thread) by executing the I<event loop> handler, and will then |
16 | (or thread) by executing the I<event loop> handler, and will then |
17 | communicate events via a callback mechanism. |
17 | communicate events via a callback mechanism. |
18 | |
18 | |
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25 | |
25 | |
26 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
26 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
27 | kqueue mechanisms for file descriptor events, relative timers, absolute |
27 | kqueue mechanisms for file descriptor events, relative timers, absolute |
28 | timers with customised rescheduling, signal events, process status change |
28 | timers with customised rescheduling, signal events, process status change |
29 | events (related to SIGCHLD), and event watchers dealing with the event |
29 | events (related to SIGCHLD), and event watchers dealing with the event |
30 | loop mechanism itself (idle, prepare and check watchers). |
30 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
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31 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
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32 | it to libevent for example). |
31 | |
33 | |
32 | =head1 CONVENTIONS |
34 | =head1 CONVENTIONS |
33 | |
35 | |
34 | Libev is very configurable. In this manual the default configuration |
36 | Libev is very configurable. In this manual the default configuration |
35 | will be described, which supports multiple event loops. For more info |
37 | will be described, which supports multiple event loops. For more info |
36 | about various configuraiton options please have a look at the file |
38 | about various configuration options please have a look at the file |
37 | F<README.embed> in the libev distribution. If libev was configured without |
39 | F<README.embed> in the libev distribution. If libev was configured without |
38 | support for multiple event loops, then all functions taking an initial |
40 | support for multiple event loops, then all functions taking an initial |
39 | argument of name C<loop> (which is always of type C<struct ev_loop *>) |
41 | argument of name C<loop> (which is always of type C<struct ev_loop *>) |
40 | will not have this argument. |
42 | will not have this argument. |
41 | |
43 | |
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61 | you linked against by calling the functions C<ev_version_major> and |
63 | you linked against by calling the functions C<ev_version_major> and |
62 | C<ev_version_minor>. If you want, you can compare against the global |
64 | C<ev_version_minor>. If you want, you can compare against the global |
63 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
65 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
64 | version of the library your program was compiled against. |
66 | version of the library your program was compiled against. |
65 | |
67 | |
66 | Usually, its a good idea to terminate if the major versions mismatch, |
68 | Usually, it's a good idea to terminate if the major versions mismatch, |
67 | as this indicates an incompatible change. Minor versions are usually |
69 | as this indicates an incompatible change. Minor versions are usually |
68 | compatible to older versions, so a larger minor version alone is usually |
70 | compatible to older versions, so a larger minor version alone is usually |
69 | not a problem. |
71 | not a problem. |
70 | |
72 | |
71 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
73 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
72 | |
74 | |
73 | Sets the allocation function to use (the prototype is similar to the |
75 | Sets the allocation function to use (the prototype is similar to the |
74 | realloc function). It is used to allocate and free memory (no surprises |
76 | realloc C function, the semantics are identical). It is used to allocate |
75 | here). If it returns zero when memory needs to be allocated, the library |
77 | and free memory (no surprises here). If it returns zero when memory |
76 | might abort or take some potentially destructive action. The default is |
78 | needs to be allocated, the library might abort or take some potentially |
77 | your system realloc function. |
79 | destructive action. The default is your system realloc function. |
78 | |
80 | |
79 | You could override this function in high-availability programs to, say, |
81 | You could override this function in high-availability programs to, say, |
80 | free some memory if it cannot allocate memory, to use a special allocator, |
82 | free some memory if it cannot allocate memory, to use a special allocator, |
81 | or even to sleep a while and retry until some memory is available. |
83 | or even to sleep a while and retry until some memory is available. |
82 | |
84 | |
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84 | |
86 | |
85 | Set the callback function to call on a retryable syscall error (such |
87 | Set the callback function to call on a retryable syscall error (such |
86 | as failed select, poll, epoll_wait). The message is a printable string |
88 | as failed select, poll, epoll_wait). The message is a printable string |
87 | indicating the system call or subsystem causing the problem. If this |
89 | indicating the system call or subsystem causing the problem. If this |
88 | callback is set, then libev will expect it to remedy the sitution, no |
90 | callback is set, then libev will expect it to remedy the sitution, no |
89 | matter what, when it returns. That is, libev will geenrally retry the |
91 | matter what, when it returns. That is, libev will generally retry the |
90 | requested operation, or, if the condition doesn't go away, do bad stuff |
92 | requested operation, or, if the condition doesn't go away, do bad stuff |
91 | (such as abort). |
93 | (such as abort). |
92 | |
94 | |
93 | =back |
95 | =back |
94 | |
96 | |
… | |
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98 | types of such loops, the I<default> loop, which supports signals and child |
100 | types of such loops, the I<default> loop, which supports signals and child |
99 | events, and dynamically created loops which do not. |
101 | events, and dynamically created loops which do not. |
100 | |
102 | |
101 | If you use threads, a common model is to run the default event loop |
103 | If you use threads, a common model is to run the default event loop |
102 | in your main thread (or in a separate thrad) and for each thread you |
104 | in your main thread (or in a separate thrad) and for each thread you |
103 | create, you also create another event loop. Libev itself does no lockign |
105 | create, you also create another event loop. Libev itself does no locking |
104 | whatsoever, so if you mix calls to different event loops, make sure you |
106 | whatsoever, so if you mix calls to the same event loop in different |
105 | lock (this is usually a bad idea, though, even if done right). |
107 | threads, make sure you lock (this is usually a bad idea, though, even if |
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108 | done correctly, because it's hideous and inefficient). |
106 | |
109 | |
107 | =over 4 |
110 | =over 4 |
108 | |
111 | |
109 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
112 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
110 | |
113 | |
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115 | |
118 | |
116 | If you don't know what event loop to use, use the one returned from this |
119 | If you don't know what event loop to use, use the one returned from this |
117 | function. |
120 | function. |
118 | |
121 | |
119 | The flags argument can be used to specify special behaviour or specific |
122 | The flags argument can be used to specify special behaviour or specific |
120 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO) |
123 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO). |
121 | |
124 | |
122 | It supports the following flags: |
125 | It supports the following flags: |
123 | |
126 | |
124 | =over 4 |
127 | =over 4 |
125 | |
128 | |
126 | =item EVFLAG_AUTO |
129 | =item EVFLAG_AUTO |
127 | |
130 | |
128 | The default flags value. Use this if you have no clue (its the right |
131 | The default flags value. Use this if you have no clue (it's the right |
129 | thing, believe me). |
132 | thing, believe me). |
130 | |
133 | |
131 | =item EVFLAG_NOENV |
134 | =item EVFLAG_NOENV |
132 | |
135 | |
133 | If this flag bit is ored into the flag value then libev will I<not> look |
136 | If this flag bit is ored into the flag value (or the program runs setuid |
134 | at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this |
137 | or setgid) then libev will I<not> look at the environment variable |
135 | environment variable will override the flags completely. This is useful |
138 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
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139 | override the flags completely if it is found in the environment. This is |
136 | to try out specific backends to tets their performance, or to work around |
140 | useful to try out specific backends to test their performance, or to work |
137 | bugs. |
141 | around bugs. |
138 | |
142 | |
139 | =item EVMETHOD_SELECT portable select backend |
143 | =item EVMETHOD_SELECT (portable select backend) |
140 | |
144 | |
141 | =item EVMETHOD_POLL poll backend (everywhere except windows) |
145 | =item EVMETHOD_POLL (poll backend, available everywhere except on windows) |
142 | |
146 | |
143 | =item EVMETHOD_EPOLL linux only |
147 | =item EVMETHOD_EPOLL (linux only) |
144 | |
148 | |
145 | =item EVMETHOD_KQUEUE some bsds only |
149 | =item EVMETHOD_KQUEUE (some bsds only) |
146 | |
150 | |
147 | =item EVMETHOD_DEVPOLL solaris 8 only |
151 | =item EVMETHOD_DEVPOLL (solaris 8 only) |
148 | |
152 | |
149 | =item EVMETHOD_PORT solaris 10 only |
153 | =item EVMETHOD_PORT (solaris 10 only) |
150 | |
154 | |
151 | If one or more of these are ored into the flags value, then only these |
155 | If one or more of these are ored into the flags value, then only these |
152 | backends will be tried (in the reverse order as given here). If one are |
156 | backends will be tried (in the reverse order as given here). If one are |
153 | specified, any backend will do. |
157 | specified, any backend will do. |
154 | |
158 | |
… | |
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163 | |
167 | |
164 | =item ev_default_destroy () |
168 | =item ev_default_destroy () |
165 | |
169 | |
166 | Destroys the default loop again (frees all memory and kernel state |
170 | Destroys the default loop again (frees all memory and kernel state |
167 | etc.). This stops all registered event watchers (by not touching them in |
171 | etc.). This stops all registered event watchers (by not touching them in |
168 | any way whatsoever, although you cnanot rely on this :). |
172 | any way whatsoever, although you cannot rely on this :). |
169 | |
173 | |
170 | =item ev_loop_destroy (loop) |
174 | =item ev_loop_destroy (loop) |
171 | |
175 | |
172 | Like C<ev_default_destroy>, but destroys an event loop created by an |
176 | Like C<ev_default_destroy>, but destroys an event loop created by an |
173 | earlier call to C<ev_loop_new>. |
177 | earlier call to C<ev_loop_new>. |
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181 | |
185 | |
182 | You I<must> call this function after forking if and only if you want to |
186 | You I<must> call this function after forking if and only if you want to |
183 | use the event library in both processes. If you just fork+exec, you don't |
187 | use the event library in both processes. If you just fork+exec, you don't |
184 | have to call it. |
188 | have to call it. |
185 | |
189 | |
186 | The function itself is quite fast and its usually not a problem to call |
190 | The function itself is quite fast and it's usually not a problem to call |
187 | it just in case after a fork. To make this easy, the function will fit in |
191 | it just in case after a fork. To make this easy, the function will fit in |
188 | quite nicely into a call to C<pthread_atfork>: |
192 | quite nicely into a call to C<pthread_atfork>: |
189 | |
193 | |
190 | pthread_atfork (0, 0, ev_default_fork); |
194 | pthread_atfork (0, 0, ev_default_fork); |
191 | |
195 | |
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198 | =item unsigned int ev_method (loop) |
202 | =item unsigned int ev_method (loop) |
199 | |
203 | |
200 | Returns one of the C<EVMETHOD_*> flags indicating the event backend in |
204 | Returns one of the C<EVMETHOD_*> flags indicating the event backend in |
201 | use. |
205 | use. |
202 | |
206 | |
203 | =item ev_tstamp = ev_now (loop) |
207 | =item ev_tstamp ev_now (loop) |
204 | |
208 | |
205 | Returns the current "event loop time", which is the time the event loop |
209 | Returns the current "event loop time", which is the time the event loop |
206 | got events and started processing them. This timestamp does not change |
210 | got events and started processing them. This timestamp does not change |
207 | as long as callbacks are being processed, and this is also the base time |
211 | as long as callbacks are being processed, and this is also the base time |
208 | used for relative timers. You can treat it as the timestamp of the event |
212 | used for relative timers. You can treat it as the timestamp of the event |
… | |
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217 | If the flags argument is specified as 0, it will not return until either |
221 | If the flags argument is specified as 0, it will not return until either |
218 | no event watchers are active anymore or C<ev_unloop> was called. |
222 | no event watchers are active anymore or C<ev_unloop> was called. |
219 | |
223 | |
220 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
224 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
221 | those events and any outstanding ones, but will not block your process in |
225 | those events and any outstanding ones, but will not block your process in |
222 | case there are no events. |
226 | case there are no events and will return after one iteration of the loop. |
223 | |
227 | |
224 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
228 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
225 | neccessary) and will handle those and any outstanding ones. It will block |
229 | neccessary) and will handle those and any outstanding ones. It will block |
226 | your process until at least one new event arrives. |
230 | your process until at least one new event arrives, and will return after |
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231 | one iteration of the loop. |
227 | |
232 | |
228 | This flags value could be used to implement alternative looping |
233 | This flags value could be used to implement alternative looping |
229 | constructs, but the C<prepare> and C<check> watchers provide a better and |
234 | constructs, but the C<prepare> and C<check> watchers provide a better and |
230 | more generic mechanism. |
235 | more generic mechanism. |
231 | |
236 | |
232 | =item ev_unloop (loop, how) |
237 | =item ev_unloop (loop, how) |
233 | |
238 | |
234 | Can be used to make a call to C<ev_loop> return early. The C<how> argument |
239 | Can be used to make a call to C<ev_loop> return early (but only after it |
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240 | has processed all outstanding events). The C<how> argument must be either |
235 | must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> |
241 | C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or |
236 | call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> |
242 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
237 | calls return. |
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238 | |
243 | |
239 | =item ev_ref (loop) |
244 | =item ev_ref (loop) |
240 | |
245 | |
241 | =item ev_unref (loop) |
246 | =item ev_unref (loop) |
242 | |
247 | |
243 | Ref/unref can be used to add or remove a refcount on the event loop: Every |
248 | Ref/unref can be used to add or remove a reference count on the event |
244 | watcher keeps one reference. If you have a long-runing watcher you never |
249 | loop: Every watcher keeps one reference, and as long as the reference |
245 | unregister that should not keep ev_loop from running, ev_unref() after |
250 | count is nonzero, C<ev_loop> will not return on its own. If you have |
246 | starting, and ev_ref() before stopping it. Libev itself uses this for |
251 | a watcher you never unregister that should not keep C<ev_loop> from |
247 | example for its internal signal pipe: It is not visible to you as a user |
252 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
248 | and should not keep C<ev_loop> from exiting if the work is done. It is |
253 | example, libev itself uses this for its internal signal pipe: It is not |
249 | also an excellent way to do this for generic recurring timers or from |
254 | visible to the libev user and should not keep C<ev_loop> from exiting if |
250 | within third-party libraries. Just remember to unref after start and ref |
255 | no event watchers registered by it are active. It is also an excellent |
251 | before stop. |
256 | way to do this for generic recurring timers or from within third-party |
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257 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
252 | |
258 | |
253 | =back |
259 | =back |
254 | |
260 | |
255 | =head1 ANATOMY OF A WATCHER |
261 | =head1 ANATOMY OF A WATCHER |
256 | |
262 | |
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293 | |
299 | |
294 | As long as your watcher is active (has been started but not stopped) you |
300 | As long as your watcher is active (has been started but not stopped) you |
295 | must not touch the values stored in it. Most specifically you must never |
301 | must not touch the values stored in it. Most specifically you must never |
296 | reinitialise it or call its set method. |
302 | reinitialise it or call its set method. |
297 | |
303 | |
298 | You cna check wether an event is active by calling the C<ev_is_active |
304 | You cna check whether an event is active by calling the C<ev_is_active |
299 | (watcher *)> macro. To see wether an event is outstanding (but the |
305 | (watcher *)> macro. To see whether an event is outstanding (but the |
300 | callback for it has not been called yet) you cna use the C<ev_is_pending |
306 | callback for it has not been called yet) you cna use the C<ev_is_pending |
301 | (watcher *)> macro. |
307 | (watcher *)> macro. |
302 | |
308 | |
303 | Each and every callback receives the event loop pointer as first, the |
309 | Each and every callback receives the event loop pointer as first, the |
304 | registered watcher structure as second, and a bitset of received events as |
310 | registered watcher structure as second, and a bitset of received events as |
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400 | This section describes each watcher in detail, but will not repeat |
406 | This section describes each watcher in detail, but will not repeat |
401 | information given in the last section. |
407 | information given in the last section. |
402 | |
408 | |
403 | =head2 struct ev_io - is my file descriptor readable or writable |
409 | =head2 struct ev_io - is my file descriptor readable or writable |
404 | |
410 | |
405 | I/O watchers check wether a file descriptor is readable or writable |
411 | I/O watchers check whether a file descriptor is readable or writable |
406 | in each iteration of the event loop (This behaviour is called |
412 | in each iteration of the event loop (This behaviour is called |
407 | level-triggering because you keep receiving events as long as the |
413 | level-triggering because you keep receiving events as long as the |
408 | condition persists. Remember you cna stop the watcher if you don't want to |
414 | condition persists. Remember you cna stop the watcher if you don't want to |
409 | act on the event and neither want to receive future events). |
415 | act on the event and neither want to receive future events). |
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416 | |
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417 | In general you can register as many read and/or write event watchers oer |
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418 | fd as you want (as long as you don't confuse yourself). Setting all file |
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419 | descriptors to non-blocking mode is also usually a good idea (but not |
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420 | required if you know what you are doing). |
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421 | |
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422 | You have to be careful with dup'ed file descriptors, though. Some backends |
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423 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
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424 | descriptors correctly if you register interest in two or more fds pointing |
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425 | to the same file/socket etc. description. |
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426 | |
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427 | If you must do this, then force the use of a known-to-be-good backend |
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428 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
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429 | EVMETHOD_POLL). |
410 | |
430 | |
411 | =over 4 |
431 | =over 4 |
412 | |
432 | |
413 | =item ev_io_init (ev_io *, callback, int fd, int events) |
433 | =item ev_io_init (ev_io *, callback, int fd, int events) |
414 | |
434 | |
… | |
… | |
428 | The timers are based on real time, that is, if you register an event that |
448 | The timers are based on real time, that is, if you register an event that |
429 | times out after an hour and youreset your system clock to last years |
449 | times out after an hour and youreset your system clock to last years |
430 | time, it will still time out after (roughly) and hour. "Roughly" because |
450 | time, it will still time out after (roughly) and hour. "Roughly" because |
431 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
451 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
432 | monotonic clock option helps a lot here). |
452 | monotonic clock option helps a lot here). |
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453 | |
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454 | The relative timeouts are calculated relative to the C<ev_now ()> |
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455 | time. This is usually the right thing as this timestamp refers to the time |
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456 | of the event triggering whatever timeout you are modifying/starting. If |
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457 | you suspect event processing to be delayed and you *need* to base the timeout |
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458 | ion the current time, use something like this to adjust for this: |
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459 | |
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460 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
433 | |
461 | |
434 | =over 4 |
462 | =over 4 |
435 | |
463 | |
436 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
464 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
437 | |
465 | |
… | |
… | |
467 | state where you do not expect data to travel on the socket, you can stop |
495 | state where you do not expect data to travel on the socket, you can stop |
468 | the timer, and again will automatically restart it if need be. |
496 | the timer, and again will automatically restart it if need be. |
469 | |
497 | |
470 | =back |
498 | =back |
471 | |
499 | |
472 | =head2 ev_periodic |
500 | =head2 ev_periodic - to cron or not to cron it |
473 | |
501 | |
474 | Periodic watchers are also timers of a kind, but they are very versatile |
502 | Periodic watchers are also timers of a kind, but they are very versatile |
475 | (and unfortunately a bit complex). |
503 | (and unfortunately a bit complex). |
476 | |
504 | |
477 | Unlike ev_timer's, they are not based on real time (or relative time) |
505 | Unlike ev_timer's, they are not based on real time (or relative time) |
… | |
… | |
567 | |
595 | |
568 | =head2 ev_signal - signal me when a signal gets signalled |
596 | =head2 ev_signal - signal me when a signal gets signalled |
569 | |
597 | |
570 | Signal watchers will trigger an event when the process receives a specific |
598 | Signal watchers will trigger an event when the process receives a specific |
571 | signal one or more times. Even though signals are very asynchronous, libev |
599 | signal one or more times. Even though signals are very asynchronous, libev |
572 | will try its best to deliver signals synchronously, i.e. as part of the |
600 | will try it's best to deliver signals synchronously, i.e. as part of the |
573 | normal event processing, like any other event. |
601 | normal event processing, like any other event. |
574 | |
602 | |
575 | You cna configure as many watchers as you like per signal. Only when the |
603 | You cna configure as many watchers as you like per signal. Only when the |
576 | first watcher gets started will libev actually register a signal watcher |
604 | first watcher gets started will libev actually register a signal watcher |
577 | with the kernel (thus it coexists with your own signal handlers as long |
605 | with the kernel (thus it coexists with your own signal handlers as long |