'Seek to an offset in the file.'

def Seek(self, offset, whence=0):

    if (whence == 0):
        self.offset = offset
    elif (whence == 1):
        self.offset += offset
    elif (whence == 2):
        self.offset = (self.size + offset)
    else:
        raise RuntimeError(('Illegal    whence    value    %s' % whence))
