anchor.diff:  
   int gfMultiply(int x, int y) {
     if (x == 0 || y == 0) return 0;
  -  return GF_EXP[GF_LOG[x] + GF_LOG[y]];
  +  return _GF_EXP[_GF_LOG[x] + _GF_LOG[y]];
   }
   
   /**
  
positive.code:   if (x == 0) {
      return 0;
    }
    return GF_EXP[GF_LOG[x] + 255 - GF_LOG[y]];
  }
  
  int gfInverse(int y) {
  
negative.code:     if (x & 256 == 256) {
        x ^= prim;
      }
      _GF_EXP[i] = x;
      _GF_LOG[x] = i;
    }
    for (int i = 255; i < 512; i++) {
      _GF_EXP[i] = _GF_EXP[i - 255];
    }
  }
  