… | |
… | |
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). It also is quite |
30 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
31 | fast (see a L<benchmark|http://libev.schmorp.de/bench.html> comparing it |
31 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
32 | to libevent). |
32 | it to libevent for example). |
33 | |
33 | |
34 | =head1 CONVENTIONS |
34 | =head1 CONVENTIONS |
35 | |
35 | |
36 | Libev is very configurable. In this manual the default configuration |
36 | Libev is very configurable. In this manual the default configuration |
37 | will be described, which supports multiple event loops. For more info |
37 | will be described, which supports multiple event loops. For more info |
38 | about various configuraiton options please have a look at the file |
38 | about various configuration options please have a look at the file |
39 | 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 |
40 | support for multiple event loops, then all functions taking an initial |
40 | support for multiple event loops, then all functions taking an initial |
41 | 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 *>) |
42 | will not have this argument. |
42 | will not have this argument. |
43 | |
43 | |
… | |
… | |
71 | not a problem. |
71 | not a problem. |
72 | |
72 | |
73 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
73 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
74 | |
74 | |
75 | 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 |
76 | 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 |
77 | 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 |
78 | might abort or take some potentially destructive action. The default is |
78 | needs to be allocated, the library might abort or take some potentially |
79 | your system realloc function. |
79 | destructive action. The default is your system realloc function. |
80 | |
80 | |
81 | You could override this function in high-availability programs to, say, |
81 | You could override this function in high-availability programs to, say, |
82 | 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, |
83 | 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. |
84 | |
84 | |
… | |
… | |
86 | |
86 | |
87 | 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 |
88 | 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 |
89 | indicating the system call or subsystem causing the problem. If this |
89 | indicating the system call or subsystem causing the problem. If this |
90 | 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 |
91 | 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 |
92 | 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 |
93 | (such as abort). |
93 | (such as abort). |
94 | |
94 | |
95 | =back |
95 | =back |
96 | |
96 | |
… | |
… | |
100 | 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 |
101 | events, and dynamically created loops which do not. |
101 | events, and dynamically created loops which do not. |
102 | |
102 | |
103 | 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 |
104 | 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 |
105 | 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 |
106 | 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 |
107 | 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 |
|
|
108 | done correctly, because its hideous and inefficient). |
108 | |
109 | |
109 | =over 4 |
110 | =over 4 |
110 | |
111 | |
111 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
112 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
112 | |
113 | |
… | |
… | |
117 | |
118 | |
118 | 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 |
119 | function. |
120 | function. |
120 | |
121 | |
121 | 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 |
122 | 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). |
123 | |
124 | |
124 | It supports the following flags: |
125 | It supports the following flags: |
125 | |
126 | |
126 | =over 4 |
127 | =over 4 |
127 | |
128 | |
… | |
… | |
130 | 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 |
131 | thing, believe me). |
132 | thing, believe me). |
132 | |
133 | |
133 | =item EVFLAG_NOENV |
134 | =item EVFLAG_NOENV |
134 | |
135 | |
135 | 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 |
136 | at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this |
137 | or setgid) then libev will I<not> look at the environment variable |
137 | environment variable will override the flags completely. This is useful |
138 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
|
|
139 | override the flags completely if it is found in the environment. This is |
138 | 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 |
139 | bugs. |
141 | around bugs. |
140 | |
142 | |
141 | =item EVMETHOD_SELECT portable select backend |
143 | =item EVMETHOD_SELECT portable select backend |
142 | |
144 | |
143 | =item EVMETHOD_POLL poll backend (everywhere except windows) |
145 | =item EVMETHOD_POLL poll backend (everywhere except windows) |
144 | |
146 | |
… | |
… | |
408 | in each iteration of the event loop (This behaviour is called |
410 | in each iteration of the event loop (This behaviour is called |
409 | level-triggering because you keep receiving events as long as the |
411 | level-triggering because you keep receiving events as long as the |
410 | 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 |
411 | act on the event and neither want to receive future events). |
413 | act on the event and neither want to receive future events). |
412 | |
414 | |
|
|
415 | In general you can register as many read and/or write event watchers oer |
|
|
416 | fd as you want (as long as you don't confuse yourself). Setting all file |
|
|
417 | descriptors to non-blocking mode is also usually a good idea (but not |
|
|
418 | required if you know what you are doing). |
|
|
419 | |
|
|
420 | You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
421 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
422 | descriptors correctly if you register interest in two or more fds pointing |
|
|
423 | to the same file/socket etc. description. |
|
|
424 | |
|
|
425 | If you must do this, then force the use of a known-to-be-good backend |
|
|
426 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
|
|
427 | EVMETHOD_POLL). |
|
|
428 | |
413 | =over 4 |
429 | =over 4 |
414 | |
430 | |
415 | =item ev_io_init (ev_io *, callback, int fd, int events) |
431 | =item ev_io_init (ev_io *, callback, int fd, int events) |
416 | |
432 | |
417 | =item ev_io_set (ev_io *, int fd, int events) |
433 | =item ev_io_set (ev_io *, int fd, int events) |