> From: [EMAIL PROTECTED]
>
> The point I was trying to make (poorly) was that io (and other
> variables) that may universally declared volatile, may in fact have
> values that need to be used in a "non-volatile" fashion.
>
> You have same problem with unrollable operations such as:
>
> if (ioport == 1)
> else if (ioport == 2)
> else if (ioport == 99)
>
> So, copy to temporary seems a more general solution - if "non volatile"
> access is required.
In cases such as these, a copy to a temporary would be required -- the value of
the port could change between tests. If you fail to use a temporary, not only
are you generating multiple reads to the port, but you are also opening a
window where all the tests could fail when at least one of them should succeed.
Another solution in this particular case would be to replace the if-else
cascade with a switch.
switch (ioport)
{
case 1: ...
case 2: ...
case 99: ...
}
This is (IMHO) a closer abstraction of what you actually want done. Though you
have to be clever if you're going to mask bits like the original example. In
which case an if-else cascade using a temporary would be better.
Regards,
-=Dave
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