<=>

VALUE
rb_big_cmp(VALUE x, VALUE y)
{
    long xlen = RBIGNUM_LEN(x);
    BDIGIT *xds, *yds;

    switch (TYPE(y)) {
      case T_FIXNUM:
        y = rb_int2big(FIX2LONG(y));
        break;

      case T_BIGNUM:
        break;

      case T_FLOAT:
        {
            double a = RFLOAT_VALUE(y);

            if (isinf(a)) {
                if (a > 0.0) return INT2FIX(-1);
                else return INT2FIX(1);
            }
            return rb_dbl_cmp(rb_big2dbl(x), a);
        }

      default:
        return rb_num_coerce_cmp(x, y, rb_intern("<=>"));
    }

    if (RBIGNUM_SIGN(x) > RBIGNUM_SIGN(y)) return INT2FIX(1);
    if (RBIGNUM_SIGN(x) < RBIGNUM_SIGN(y)) return INT2FIX(-1);
    if (xlen < RBIGNUM_LEN(y))
        return (RBIGNUM_SIGN(x)) ? INT2FIX(-1) : INT2FIX(1);
    if (xlen > RBIGNUM_LEN(y))
        return (RBIGNUM_SIGN(x)) ? INT2FIX(1) : INT2FIX(-1);

    xds = BDIGITS(x);
    yds = BDIGITS(y);

    while(xlen-- && (xds[xlen]==yds[xlen]));
    if (-1 == xlen) return INT2FIX(0);
    return (xds[xlen] > yds[xlen]) ?
        (RBIGNUM_SIGN(x) ? INT2FIX(1) : INT2FIX(-1)) :
            (RBIGNUM_SIGN(x) ? INT2FIX(-1) : INT2FIX(1));
}