def METHOD_NAME(qed, pos, *args):
    '''zero-cluster <pos> [<n>] - Zero data clusters'''
    pos, n = int(pos), 1
    if args:
        if len(args) != 1:
            err('expected one argument')
        n = int(args[0])
    for i in xrange(n):
        l1_index = pos // qed.header['cluster_size'] // len(qed.l1_table)
        if qed.l1_table[l1_index] == 0:
            err('no l2 table allocated')
        l2_offset = qed.l1_table[l1_index]
        l2_table = qed.read_table(l2_offset)
        l2_index = (pos // qed.header['cluster_size']) % len(qed.l1_table)
        l2_table[l2_index] = 1 # zero the data cluster
        qed.write_table(l2_offset, l2_table)
        pos += qed.header['cluster_size']