 conversions
    var BI_RM = "0123456789abcdefghijklmnopqrstuvwxyz";
    var BI_RC = new Array();
    var rr, vv;
    rr = "0".charCodeAt(0);
    for (vv = 0; vv <= 9; ++vv) BI_RC[rr++] = vv;
    rr = "a".charCodeAt(0);
    for (vv = 10; vv < 36; ++vv) BI_RC[rr++] = vv;
    rr = "A".charCodeAt(0);
    for (vv = 10; vv < 36; ++vv) BI_RC[rr++] = vv;

    function int2char(n) {
        return BI_RM.charAt(n);
    }

    function intAt(s, i) {
        var c = BI_RC[s.charCodeAt(i)];
        return (c == null) ?