函数ut_2_log

/*************************************************************//**
Calculates fast the 2-logarithm of a number, rounded upward to an
integer.
@return    logarithm in the base 2, rounded upward */
UNIV_INLINE
ulint
ut_2_log(
/*=====*/
    ulint    n)    /*!< in: number != 0 */
{
    ulint    res;

    res = 0;

    ut_ad(n > 0);

    n = n - 1;

    for (;;) {
        n = n / 2;

        if (n == 0) {
            break;
        }

        res++;
    }

    return(res + 1);
}