Converting huge numbers for Decimal to Hexadecimal and visa versa

Fu Manchu

Hi all,:) i have been trying to create some function that take the Decimal datatype to convert decimal to hexadecimal and the reverse. my code at present uses the long datatype which go up to 9.2 E+18. Currently i am working with larger numbers. This is my code: Private Function ConvertDecimalToHexadecimal(ByVal number As Decimal) Dim converted As String Dim value As Long = Long.Parse(number) converted = value.ToString("X") Return converted End Function Private Function ConvertHexadecimalToDecimal(ByVal number As String) Dim txt As String Dim value As Decimal Dim converted As String txt = UCase(Trim(number)) If txt.StartsWith("&H") Then txt = txt.Substring(2) value = long.Parse(txt, Globalization.NumberStyles.HexNumber) converted = value.ToString() Return converted End Function Is there some way of making this work for numbers up to the decimal datatype of 1.79 E+308 or if anyone knows of another way? Thanks

Johan Hakkesteegt

Hi, According to Microsoft's .NET documentation, you'll have to either use the Double type instead of Long or round you numbers to a more manageable size, before handling them. On a less helpful note, you could make your function a little smaller like so: Private Function ConvertDecimalToHexadecimal(ByVal number As Decimal) As String Return Double.Parse(number).ToString("X") End Function Private Function ConvertHexadecimalToDecimal(ByVal number As String) As String If UCase(Trim(number)).StartsWith("&H") Then number = number.Substring(2) Return Double.Parse(number, Globalization.NumberStyles.HexNumber).ToString End Function Hope it helps, Johan

My advice is free, and you may get what you paid for.

TwoFaced

I couldn't find any built in functions to do such large conversions. However, I had some code to convert Hex to Dec and vice versa. I made some modifications to ensure the conversion would work with the largest decimal number allowed. Here is the code which I believe works perfectly. If you discover a problem let me know. Hope this helps.

Public Class Form1
'Test conversion of the largest allowed decimal value
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim msg As String = "MaxDecimal: " & Decimal.MaxValue.ToString & _
vbCrLf & "MaxDecimal as Hex: " & DecToHex(Decimal.MaxValue).ToUpper & _
vbCrLf & "Hex converted back: " & HexToDec(DecToHex(Decimal.MaxValue)).ToString

    MsgBox(msg)
End Sub

'---MAIN CONVERSION FUNCTIONS---

'Converts a decimal type to it's Hex value
'Does not support fractional numbers, so don't pass them :)
'Actually they just get rounded so nothing to worry about.
Private Function DecToHex(ByVal number As Decimal) As String
    number = Decimal.Round(number)
    Dim result As New System.Text.StringBuilder

    Do While number > 0
        Dim remainder As Integer = number Mod 16

        number = number / 16D
        number = Decimal.Truncate(number)
        result.Insert(0, DecToHexChar(remainder))
    Loop
    Return result.ToString
End Function

'Converts a string of Hex characters to it's decimal equivalent
'Does not provide any validation.  String must have nothing but
'valid Hex values.  Although no errors should occur.
Private Function HexToDec(ByVal hex As String) As Decimal
    Dim result As Decimal

    For i As Decimal = 0 To hex.Length - 1
        Dim chr As Char = hex.Chars(i)
        result += (HexCharToDec(chr) \* Pow(16, hex.Length - 1 - i))
    Next
    Return result
End Function

'---HELPER FUNCTIONS---

'Converts a Decimal value 0 to 15 to it's Hex character equivalent
'If number is anything else it returns String.Empty
Private Function DecToHexChar(ByVal number As Integer) As String
    If number < 10 Then Return number
    Select Case number
        Case 10 : Return "A"
        Case 11 : Return "B"
        Case 12 : Return "C"
        Case 13 : Return "D"
        Case 14 : Return "E"
        Case 15 : Return "F"
    End Select
    Return String