code: def _adjust(a, a_offset, b):
      
      x = (b[-1] & 0xFF) + (a[a_offset + len(b) - 1] & 0xFF) + 1
      a[a_offset + len(b) - 1] = ctypes.c_ubyte(x).value
      x >>= 8
  
      for i in range(len(b)-2, -1, -1):
          x += (b[i] & 0xFF) + (a[a_offset + i] & 0xFF)
          a[a_offset + i] = ctypes.c_ubyte(x).value
          x >>= 8
docs: a = bytearray
      a_offset = int
      b = bytearray