Hi Andrew, --- Andrew Schweitzer <a.schweitzer.grps@gmail.com> wrote: <snip>
Select is passed a list of all active sockets plus a special, "dummy" socket. Select_reactor, via a socket_select_interrupter object, is both client and server on this special dummy socket.
On posix platforms this is a pipe, rather than a socket. Otherwise your statements seem correct.
Assuming all of that is correct, can you explain what the code in socket_ops::select() does that checks if all sockets are null and if so calls ::Sleep()?
To make select on Windows behave like select on other platforms :)
I sort of expect I've missed something, but it looks like dead code. with the prescence of the interrupter and its dummy socket, the socket list will never be null. Also, if they were null, I'm not sure Sleep would work very well. For one thing, it's not interruptable, so if the only thing is a large timer, any new additions of sockets or timers would have to wait for the large timer to complete before they could be added. For another, it looks like if there were no timers running, it would essentially be polling 1/ms for sockets + timers.
The socket_ops::select() function is also used to implement the blocking deadline_timer::wait() operation, which doesn't pass any sockets to select at all. But in terms of the select_reactor, you're right that the particular code path isn't used (and in fact the compiler ought to be able to easily optimise it out). Cheers, Chris