Re: A89: Filling a Byte in C

To: <assembly-89@lists.ticalc.org>
Subject: Re: A89: Filling a Byte in C
From: "mheckenbach" <mheckenbach@yahoo.com>
Date: Sun, 14 May 2000 22:44:33 -0500
References: <Pine.SOL.4.21.0005141957540.17705-100000@conquest.OCF.Berkeley.EDU>
Reply-To: assembly-89@lists.ticalc.org


I think this would work:

byte GetByteMask(char Start, char End)
{
    return (1 << (End + 1)) - (1 << Start);
}



>
>
> On Sun, 14 May 2000, Sebastian Reichelt wrote:
>
> >
> > Hi,
> >
> > does anyone know how to fill a byte from bit x to bit y with ones in C,
and
> > fill the rest with zeros.  Here's my solution, but I'm sure there is a
much
> > better way:
>
> I'm not sure if this way is better, but it is certainly smaller:
>
> char GetByteMask(char start, char end)
> {
>     char x = 0;
>     int y;
>     for (y = start; y <= end; y++)
>         x |= 1 << y;
>     return x;
> }
>
> In case you can't guess:
>
> x |= y      means set X to X logical or Y
> x << y      means shift x left y bits (multiply x by 2^y)
>




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References:

Re: A89: Filling a Byte in C

From: Patrick Davidson <pad@ocf.Berkeley.EDU>