The a64l and l64a functions are used to maintain numbers stored
    in base-64 ASCII characters as follows:

    o  a64l converts a character string to a long integer.

    o  l64a converts a long integer to a character string.

    Each character used for storing a long integer represents a
    numeric value from 0 through 63. Up to six characters can be
    used to represent a long integer.

    The characters are translated as follows:

    o  A period (.)  represents 0.

    o  A slash (/)  represents 1.

    o  The numbers 0 through 9 represent 2 through 11.

    o  Uppercase letters A through Z represent 12 through 37.

    o  Lowercase letters a through z represent 38 through 63.

    The a64l function takes a pointer to a base-64 representation,
    in which the first digit is the least significant, and returns
    a corresponding long value. If the string pointed to by the s
    parameter exceeds six characters, a64l uses only the first six
    characters.

    If the first six characters of the string contain a null
    terminator, a64l uses only characters preceding the null
    terminator.

    The a64l function translates a character string from left to
    right with the least significant number on the left, decoding
    each character as a 6-bit base-64 number.

    If s is the NULL pointer or if the string pointed to by s was
    not generated by a previous call to l64a, the behavior of a64l is
    unspecified.

    See also l64a.