static VALUE
rb_ary_uniq_bang(ary)
    VALUE ary;
{
    VALUE hash, v, vv;
    long i, j;

    hash = ary_make_hash(ary, 0);

    if (RARRAY(ary)->len == RHASH(hash)->tbl->num_entries) {
        return Qnil;
    }
    for (i=j=0; i<RARRAY(ary)->len; i++) {
        v = vv = rb_ary_elt(ary, i);
        if (st_delete(RHASH(hash)->tbl, (st_data_t*)&vv, 0)) {
            rb_ary_store(ary, j++, v);
        }
    }
    RARRAY(ary)->len = j;

    return ary;
}