Binary to Decimal

[moonbase]

I need to convert a binary number, read from a text file, to it's decimal equivalent. It's in two's complement format, i.e can be negative.
Does anybody have a suitable routine or can anyone point me in the right direction?

Many thanks

 

[moonbase]

Thanks, this is along the right lines but when a say the right most byte is 5F, I don't mean a string of 2 ascii characters, I mean one byte, 8 bits. This can represented in this discussion as hex 5F or binary 0101 1111.
To get your idea to work I need to create an ascii string of 2 characters "5" and "F" from the byte. How do I do that?
The next problem is the number to be converted consists of 8 bytes, e.g. 00 00 00 00 00 00 00 5F.
Thanks

 

[strongm]

Right, so you've got an 8-byte 2s-complement number? Big-endian? Little-endian?

 

[moonbase]

Big-endian

 

[ArtieChoke]

Okay, I'm close, but it'll give you a starting point. Read each set of eight bytes into a byte array and process:

    Dim i As Integer
    Dim dec As Double
    Dim mult As Double
    Dim dbyte As Double
    Dim bytes(8) As Byte
    
'   Largest positive number 

    bytes(1) = 127
    bytes(2) = 255
    bytes(3) = 255
    bytes(4) = 255
    bytes(5) = 255
    bytes(6) = 255
    bytes(7) = 255
    bytes(8) = 255
    
'   Largest negative number 

'    bytes(1) = 128
'    bytes(2) = 0
'    bytes(3) = 0
'    bytes(4) = 0
'    bytes(5) = 0
'    bytes(6) = 0
'    bytes(7) = 0
'    bytes(8) = 0
    
    If (bytes(1) And 128) = 128 Then
        bytes(1) = bytes(1) And 127
        dec = -2 ^ 63
    Else
        dec = 0
    End If
    For i = 1 To 8
        mult = 256 ^ (8 - i)
        dbyte = bytes(i)
        dec = dec + dbyte * mult
    Next
    Debug.Print Format(dec, "0000000000000000000")

See this link for an explanation:

http://www.d.umn.edu/~gshute/asm/signed.html

I took a shortcut multiplying each byte by a power of 256, so the max positive and min negative come out to be the same. The max positive should be 2^63-1 and min negative -2^63.


"I think we're all Bozos on this bus!" - Firesign Theatre

 

[moonbase]

Thanks for the help guys. It actually turned out to be fairly straightforward once I'd got my head round it. But I'd have struggled without your help. This is what I ended up with:

Public Function Hex2Currency(HexCurrency As String) As Currency

    Dim s As String
    Dim i As Integer

    ' capture error
    On Error GoTo ErrorHandler
    SaveErrNum = 0

    ' intitialise
    s = "&H"
    
    ' create hex string from each char
    For i = 1 To Len(HexCurrency)
        
         ' high order nibble
        s = s & Hex((Asc(Mid(HexCurrency, i, 1)) And &HF0) / 16)
        
        ' low order nibble
        s = s & Hex(Asc(Mid(HexCurrency, i, 1)) And &HF)
        
    Next i
    
    ' hex to currency
    Hex2Currency = CCur(s)

    Exit Function
    
ErrorHandler:
    Hex2Currency = 0
    SaveErrNum = 1

End Function

As suggested, negative numbers can be handled by subtracting from the highest value.