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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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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 its 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 | |
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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 (its 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 (everywhere except windows) |
142 | |
146 | |
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293 | |
297 | |
294 | As long as your watcher is active (has been started but not stopped) you |
298 | 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 |
299 | must not touch the values stored in it. Most specifically you must never |
296 | reinitialise it or call its set method. |
300 | reinitialise it or call its set method. |
297 | |
301 | |
298 | You cna check wether an event is active by calling the C<ev_is_active |
302 | 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 |
303 | (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 |
304 | callback for it has not been called yet) you cna use the C<ev_is_pending |
301 | (watcher *)> macro. |
305 | (watcher *)> macro. |
302 | |
306 | |
303 | Each and every callback receives the event loop pointer as first, the |
307 | 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 |
308 | 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 |
404 | This section describes each watcher in detail, but will not repeat |
401 | information given in the last section. |
405 | information given in the last section. |
402 | |
406 | |
403 | =head2 struct ev_io - is my file descriptor readable or writable |
407 | =head2 struct ev_io - is my file descriptor readable or writable |
404 | |
408 | |
405 | I/O watchers check wether a file descriptor is readable or writable |
409 | I/O watchers check whether a file descriptor is readable or writable |
406 | in each iteration of the event loop (This behaviour is called |
410 | in each iteration of the event loop (This behaviour is called |
407 | level-triggering because you keep receiving events as long as the |
411 | 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 |
412 | 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). |
413 | act on the event and neither want to receive future events). |
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414 | |
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415 | In general you can register as many read and/or write event watchers oer |
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416 | fd as you want (as long as you don't confuse yourself). Setting all file |
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417 | descriptors to non-blocking mode is also usually a good idea (but not |
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418 | required if you know what you are doing). |
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419 | |
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420 | You have to be careful with dup'ed file descriptors, though. Some backends |
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421 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
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422 | descriptors correctly if you register interest in two or more fds pointing |
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423 | to the same file/socket etc. description. |
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424 | |
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425 | If you must do this, then force the use of a known-to-be-good backend |
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426 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
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427 | EVMETHOD_POLL). |
410 | |
428 | |
411 | =over 4 |
429 | =over 4 |
412 | |
430 | |
413 | =item ev_io_init (ev_io *, callback, int fd, int events) |
431 | =item ev_io_init (ev_io *, callback, int fd, int events) |
414 | |
432 | |
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467 | state where you do not expect data to travel on the socket, you can stop |
485 | 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. |
486 | the timer, and again will automatically restart it if need be. |
469 | |
487 | |
470 | =back |
488 | =back |
471 | |
489 | |
472 | =head2 ev_periodic |
490 | =head2 ev_periodic - to cron or not to cron it |
473 | |
491 | |
474 | Periodic watchers are also timers of a kind, but they are very versatile |
492 | Periodic watchers are also timers of a kind, but they are very versatile |
475 | (and unfortunately a bit complex). |
493 | (and unfortunately a bit complex). |
476 | |
494 | |
477 | Unlike ev_timer's, they are not based on real time (or relative time) |
495 | Unlike ev_timer's, they are not based on real time (or relative time) |