Re: primitive byte --> unsigned byte...best way?

|September 22, 2000) at
  11/16/2000 02:23:13 AM
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What you probably want is an UnsignedByteArray class whose essence is
something like this:

class UnsignedByteArray {

   byte array[];

   UnsignedByteArray(byte inputArray[]) { array = inputArray; }

    // fetch from the apparent unsigned byte array at arrayIndex into a
signed integer
    public int byteAt(int arrayIndex) {
         return   ( array[arrayIndex]>0 ?  array[arrayIndex] :
128+array[arrayIndex]);
    }

   // place the low order byte of the integer value back into the array at
arrayIndex
   public void setByte(int arrayIndex,int value) {
     byte source = (byte) value;
     array[arrayIndex] = source;
   }

}

If you aren't familiar with the ? and : operation of Java, you could
express byteAt
with:

   int res=0;
   if (array[arrayIndex]>0) res = array[arrayIndex];
   else res = array[arrayIndex] + 128;
   return res;

Because you are dealing with an array of bytes, "byte order" problems
don't arise.

They don't arise in general in Java anyway; Java's definitions are very
careful to preserve the illusion that it runs on a big endian virtual
machine.



Larry W. Loen  -   Senior Java and AS/400 Performance Analyst
                           Dept HP4, Rochester MN

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