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@ -28,14 +28,14 @@ kqueue mechanisms for file descriptor events, relative timers, absolute |
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timers with customised rescheduling, signal events, process status change |
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events (related to SIGCHLD), and event watchers dealing with the event |
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loop mechanism itself (idle, prepare and check watchers). It also is quite |
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fast (see a L<http://libev.schmorp.de/bench.html|benchmark> comparing it |
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to libevent). |
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fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
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it to libevent for example). |
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=head1 CONVENTIONS |
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Libev is very configurable. In this manual the default configuration |
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will be described, which supports multiple event loops. For more info |
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about various configuraiton options please have a look at the file |
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about various configuration options please have a look at the file |
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F<README.embed> in the libev distribution. If libev was configured without |
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support for multiple event loops, then all functions taking an initial |
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argument of name C<loop> (which is always of type C<struct ev_loop *>) |
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@ -73,10 +73,10 @@ not a problem. |
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=item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
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Sets the allocation function to use (the prototype is similar to the |
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realloc function). It is used to allocate and free memory (no surprises |
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here). If it returns zero when memory needs to be allocated, the library |
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might abort or take some potentially destructive action. The default is |
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your system realloc function. |
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realloc C function, the semantics are identical). It is used to allocate |
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and free memory (no surprises here). If it returns zero when memory |
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needs to be allocated, the library might abort or take some potentially |
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destructive action. The default is your system realloc function. |
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You could override this function in high-availability programs to, say, |
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free some memory if it cannot allocate memory, to use a special allocator, |
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@ -88,7 +88,7 @@ Set the callback function to call on a retryable syscall error (such |
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as failed select, poll, epoll_wait). The message is a printable string |
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indicating the system call or subsystem causing the problem. If this |
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callback is set, then libev will expect it to remedy the sitution, no |
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matter what, when it returns. That is, libev will geenrally retry the |
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matter what, when it returns. That is, libev will generally retry the |
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requested operation, or, if the condition doesn't go away, do bad stuff |
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(such as abort). |
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@ -102,9 +102,10 @@ events, and dynamically created loops which do not. |
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If you use threads, a common model is to run the default event loop |
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in your main thread (or in a separate thrad) and for each thread you |
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create, you also create another event loop. Libev itself does no lockign |
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whatsoever, so if you mix calls to different event loops, make sure you |
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lock (this is usually a bad idea, though, even if done right). |
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create, you also create another event loop. Libev itself does no locking |
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whatsoever, so if you mix calls to the same event loop in different |
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threads, make sure you lock (this is usually a bad idea, though, even if |
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done correctly, because its hideous and inefficient). |
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=over 4 |
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@ -119,7 +120,7 @@ If you don't know what event loop to use, use the one returned from this |
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function. |
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The flags argument can be used to specify special behaviour or specific |
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backends to use, and is usually specified as 0 (or EVFLAG_AUTO) |
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backends to use, and is usually specified as 0 (or EVFLAG_AUTO). |
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It supports the following flags: |
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@ -132,11 +133,12 @@ thing, believe me). |
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=item EVFLAG_NOENV |
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If this flag bit is ored into the flag value then libev will I<not> look |
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at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this |
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environment variable will override the flags completely. This is useful |
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to try out specific backends to tets their performance, or to work around |
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bugs. |
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If this flag bit is ored into the flag value (or the program runs setuid |
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or setgid) then libev will I<not> look at the environment variable |
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C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
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override the flags completely if it is found in the environment. This is |
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useful to try out specific backends to test their performance, or to work |
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around bugs. |
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=item EVMETHOD_SELECT portable select backend |
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@ -410,6 +412,20 @@ level-triggering because you keep receiving events as long as the |
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condition persists. Remember you cna stop the watcher if you don't want to |
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act on the event and neither want to receive future events). |
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In general you can register as many read and/or write event watchers oer |
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fd as you want (as long as you don't confuse yourself). Setting all file |
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descriptors to non-blocking mode is also usually a good idea (but not |
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required if you know what you are doing). |
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You have to be careful with dup'ed file descriptors, though. Some backends |
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(the linux epoll backend is a notable example) cannot handle dup'ed file |
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descriptors correctly if you register interest in two or more fds pointing |
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to the same file/socket etc. description. |
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If you must do this, then force the use of a known-to-be-good backend |
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(at the time of this writing, this includes only EVMETHOD_SELECT and |
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EVMETHOD_POLL). |
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=over 4 |
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=item ev_io_init (ev_io *, callback, int fd, int events) |
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Marc Alexander Lehmann
15 years ago