ser*.[hc] cleanup

[Todd Whitesel]

> In going through this I noticed that ser-unix.c implements non-blocking
> reads using either select() or TERMIO/TERMIOS calls (?).

Yes! The VMIN/VTIME parameters let you do all kinds of cool stuff on the
serial port, like block until a burst of characters comes in, returning from
the read() as soon as the line goes quiet for some fraction of a second. Used
properly, it handily beats a select() implementation -- unless you need the
extra flexibility of select() of course.

> I'm wondering if the TERMIO/TERMIOS code that causes timeouts is now
> redundant.  It would appear that we're assuming select() anyway (c.f.
> event-loop.c).  That would allow me to be even more ruthless :-)

Around 1996 or so, I did a survey of all the obscure machines at Green Hills
in an attempt to resolve this very question. They were all okay except:

There is at least one old sysV variant (SCO, 3.2something I think) that
has select() for sockets ONLY, and doesn't allow select() on serial ports.
Worse, it didn't even have FIONREAD. I ended up simulating that with a V7
ioctl I spotted in the system headers, but it wasn't pretty -- I had to
preserve the gross "call alarm, then read, and maybe longjmp out of a signal
handler to abort the read" method just for this one host.

I'd say we should look at select() like ANSI C -- we've waited long enough,
let's just do it and wait for someone to cry uncle.

-- 
Todd Whitesel
toddpw @ windriver.com