RE: [C400-L] add long strings as unsigned integers

["Bob Crothers" <bob@xxxxxxxxxxxxxx>]

Gene,

Without actually writing the program, below is how I would
approach it:

bool Add3Values(BYTE val1, BYTE val2, BYTE val3, BYTE *Result,
BYTE *CarryResult)
{
  // Add the 3 values together coming up with Result and
CarryResult
  // If CarryResult overflows, return false, else return true
  //  CarryResult happens if adding x'FF' + x'FF' + x'FF' 
}

AddStrings(BYTE *Str1, BYTE *Str2, BYTE *Result, int resLen)
{
        // First, right adjust Str1 and Str2 making them the same
length.

        // Next, make sure that resLen is at least 1 byte larger
then the largest
        // of Str1 & Str2

BYTE CarryValue = 0;

For (int x = LargestLenOfStr1and2; x > 0; x--)
        {
        if (!Add3Values(Str1[x], Str2[x], &Result[x],
&CarryValue))
                {
                printf("Overflow has Overflowed!  Croaking");
                exit(-1);
                }
        }

        // Now do something with Result.
}

Bob Crothers
  

> -----Original Message-----
> From: c400-l-bounces@xxxxxxxxxxxx 
> [mailto:c400-l-bounces@xxxxxxxxxxxx] On Behalf Of 
> Gene_Gaunt@xxxxxxxxxxxxxxx
> Sent: Thursday, November 13, 2003 4:31 PM
> To: C400-L@xxxxxxxxxxxx
> Subject: [C400-L] add long strings as unsigned integers
> 
> 
> How would you code addition of arbitrarily wide strings in C
language?
> For example
> 
>    x'88 00 00 00 88 00 00 00 00 22 00 00 00 33 00 00 E4'
> +  x'88 00 00 00 F1 00 11 00 11 00 22 00 22 00 22 00 33'
>    ------------------------------------------------------
> =  x'10 00 00 01 79 00 11 00 11 22 22 00 22 33 22 01 17'
> 
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