if (complement) {
	Zero(tbl, 256, short);
	for (i = 0; i < tlen; i++)
	    tbl[t[i] & 0377] = -1;
	for (i = 0, j = 0; i < 256; i++) {
	    if (!tbl[i]) {
		if (j >= rlen) {
		    if (delete)
			tbl[i] = -2;
		    else if (rlen)
			tbl[i] = r[j-1] & 0377;
		    else
			tbl[i] = i;
		}
		else
		    tbl[i] = r[j++] & 0377;
	    }
	}
    }
    else {
	if (!rlen && !delete) {
	    r = t; rlen = tlen;
	}
	for (i = 0; i < 256; i++)
	    tbl[i] = -1;
	for (i = 0, j = 0; i < tlen; i++,j++) {
	    if (j >= rlen) {
		if (delete) {
		    if (tbl[t[i] & 0377] == -1)
			tbl[t[i] & 0377] = -2;
		    continue;
		}
		--j;
	    }
	    if (tbl[t[i] & 0377] == -1)
		tbl[t[i] & 0377] = r[j] & 0377;
	}
    }
    sv_free(tstr);
    sv_free(rstr);