🚀 go-pugleaf

On Wed, 17 Mar 1999 10:23:33 -0700, Doug Bath <dbath@agt.net> wrote:

>    In 4 byte words (long ints or floats) I need to swap byte 1 with byte 4 and
>byte 2 with byte 3. Thanks to your help I was able to get the following to work
>
> private int swap4(int s)
>    {
>        int tmp1, tmp2, tmp3, tmp4;
>        tmp1 = (s & 0xFF) << 24;
>        tmp4 = (s >> 24) & 0xFF;
>        tmp2 = (s  & 0x0000FF00) << 8;
>        tmp3 = (s >> 8)  & 0x0000FF00;
>        return tmp1 | tmp2 | tmp3 | tmp4;
>    }

Looks good.

>It started to make sense when I realized that &0xFF meant leave the bits the same.
>The above works for long ints and negatives such as -2048. I need to try it on
>more data and make a version for floats. I would appreciate any suggestions or
>warnings you may have about this function and thanks again for your help.

For floats you should probably read the number as an int, use your
existing integer byte swap routine (assuming the bytes need to be
swapped in the same way), then call Float.intBitsToFloat (if your
float is stored in the format that Java uses after the byte swap).


Chris Hill
Chris244@aol.com