Base Conversion

<%
    ' ASP Mathematics Library - Base Conversion
    '
    ' Copyright (c) 2008, reusablecode.blogspot.com; some rights reserved.
    '
    ' This work is licensed under the Creative Commons Attribution License. To view
    ' a copy of this license, visit http://creativecommons.org/licenses/by/3.0/ or
    ' send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California
    ' 94305, USA.
 
    ' These functions are only capable of converting to and from bases between 2 and 36.
    ' I decided not to support larger bases because the PHP equivalent base_convert function is also limited to base 36.
 
    ' From base 37 to 62, the lowercase letters of the Latin alphabet are used, but special handling would need to be added for them.
    ' The ASCII value for Z is 90. The ASCII value for a is 97. There are six other characters in between.
 
    ' Furthermore, Base64 encoding begins with the uppercase letters A-Z, followed by a-z, followed by 0-9, followed by + and /.
    ' If you want to add Base64 support, separate functions might be wise, but could still be tied into the base_convert wrapper.
 
    ' Convert from any base to decimal.
    function toDecimal(value, radix)
        dim result
        dim digit
 
        result = 0
 
        ' Prevent radix from going out of bounds.
        if radix < 2 then
            radix = 2
        elseif radix > 36 then
            radix = 36
        end if
 
        for i = 1 to Len(value)
            digit = Mid(value, i, 1)
 
            ' Convert letters to numbers.
            if not isNumeric(digit) then
                ' The letter A in any base is equal to 10 in decimal.
                ' The ASCII value of A is 65, so subtract 55 from the ASCII value to obtain the decimal value.
                digit = Asc(UCase(digit)) - 55
            else
                digit = CInt(digit)
            end if
 
            ' Return zero if any digit is out of bounds for the radix.
            if digit >= radix then
                result = 0
                exit for
            end if
 
            result = result + (digit * radix ^ (Len(value) - i))
        next
 
        toDecimal = result
    end function
 
    ' Convert from decimal to any base.
    function fromDecimal(value, radix)
        dim result
        dim digit
 
        result = ""
 
        ' Prevent radix from going out of bounds.
        if radix < 2 then
            radix = 2
        elseif radix > 36 then
            radix = 36
        end if
 
        ' Check for invalid input.
        if isNumeric(value) then
            ' Inputted value appears to be base 10. OK to proceed.
            do until value = 0
                digit = value Mod radix
 
                if digit > 9 then
                    digit = Chr(digit + 55)
                end if
 
                result = CStr(digit) & result
                value = value \ radix
            loop
        else
            ' Inputted value was NOT base 10.
            result = 0
        end if
 
        fromDecimal = result
    end function
 
    ' Convert between bases.
    function base_convert(value, sourceRadix, targetRadix)
        if sourceRadix = targetRadix then
            ' If source radix and target radix are equal, don't waste time converting.
            baseConv = value
        elseif sourceRadix = 10 then
            ' If source radix is decimal, skip converting to decimal.
            baseConv = fromDecimal(value, targetRadix)
        elseif targetRadix = 10 then
            ' If target radix is decimal, skip converting from decimal.
            baseConv = toDecimal(value, sourceRadix)
        else
            ' Convert to decimal, and then from decimal.
            baseConv = fromDecimal(toDecimal(value, sourceRadix), targetRadix)
        end if
    end function
 
    ' Convert from binary to decimal.
    function bindec(bin)
        bindec = toDecimal(bin, 2)
    end function
 
    ' Convert from decimal to binary
    function decbin(dec)
        decbin = fromDecimal(dec, 2)
    end function
 
    ' Convert from decimal to hexadecimal.
    function dechex(dec)
        ' Assume that built-in hex() function is faster.
        dechex = hex(dec)
    end function
 
    ' Convert from decimal to octal.
    function decoct(dec)
        ' Assume that built-in oct() function is faster.
        decoct = oct(dec)
    end function
 
    ' Convert from hexadecimal to decimal.
    function hexdec(hex)
        hexdec = toDecimal(hex, 16)
    end function
 
    ' Convert from octal to decimal.
    function octdec(oct)
        octdec = toDecimal(oct, 8)
    end function
%>