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Working with binary data

VBA How To

Working with binary data

by  Bong  Posted    (Edited  )
More and more, I'm using VBA (in Excel) to make tools that produce test data or analyze real data. Those data are frequently binary telemetry. I found that VBA is short on obvious binary functions (except for HEX, there are none) and so came up with some of my own (with help from the kind experts on this forum). Should this be of interest to anyone else, here are some of my most used.

1. Convert a binary string to a hex string:
Code: 
Function b2h(bstr)
'convert binary string to hex string
    cnvarr = Array("0000", "0001", "0010", "0011", _
             "0100", "0101", "0110", "0111", "1000", _
             "1001", "1010", "1011", "1100", "1101", _
             "1110", "1111")
'find number of HEX digits
    a = Len(bstr)
    ndgt = a / 4
    If (a Mod 4 > 0) Then
        MsgBox ("must be integer multiple of 4Bits")
        Exit Function
    End If
    hstr = ""
    For i = 1 To ndgt
        dgt = Mid(bstr, (i * 4) - 3, 4)
        For k = 0 To 15
            If (dgt = cnvarr(k)) Then
                ix = k
            End If
        Next
        hstr = hstr & Hex(ix)
    Next
    b2h = hstr
End Function

2. Convert a hex string to a binary string:
Code: 
Function h2b(hstr)
'convert hex string to binary string
    cnvarr = Array("0000", "0001", "0010", "0011", _
             "0100", "0101", "0110", "0111", "1000", _
             "1001", "1010", "1011", "1100", "1101", _
             "1110", "1111")
    bstr = ""
    For i = 1 To Len(hstr)
        hdgt = Mid(hstr, i, 1)
        cix = CInt("&H" & hdgt)
        bstr = bstr & cnvarr(cix)
    Next
    h2b = bstr
End Function

3. convert a binary string to a decimal number:
Code: 
Function b2d(bstr)
'convert binary string to decimal number
    numbits = Len(bstr)
    asum = 0
    For i = 1 To numbits
        asum = asum + Mid(bstr, i, 1) * 2 ^ (numbits - i)
    Next
    b2d = asum
End Function

4. convert a decimal number to IEEE floating point (32 bit; 8 hex characters) hex string:
Code: 
Function i3efp(num_in)
    s = 0
    If num_in < 0 Then s = 1
    For e = 0 To 255
        If 2 * 2 ^ (e - 127) > Abs(num_in) Then Exit For
    Next
    If e = 0 Then GoSub toosmall
    If e = 255 Then GoSub toobig
    f = (Abs(num_in) / (2 ^ (e - 127))) - 1
    f = 1 * Right(f, Len(f) - 2)
    f = (f * 10 ^ -Len(f)) / 2 ^ -23
    eh = Hex(e)
    If Len(eh) < 2 Then eh = "0" & eh
    fh = Hex(f)
    i3eb = s & h2b(eh)  '9 bits
    fb = Right(h2b(fh), 23)
    If Len(fb) < 23 Then fb = String(23 - Len(fb), "0") & fb
    i3eb = i3eb & fb    '32 bits
    i3efp = b2h(i3eb)
    Exit Function
toobig:
    i3efp = String(8, "F")
    Exit Function
toosmall:
    i3efp = String(8, "0")
    Exit Function
End Function

5. And, of course, convert a 32-bit IEEE-formatted hex string to a decimal number:
Code: 
Function i3e2d(hstr)
    If Len(hstr) <> 8 Then
        i3e2d = "invalid input"
        Exit Function
    End If
    bstr = h2b(hstr)
    sgnbit = Left(bstr, 1)
    s = (-1) ^ sgnbit
    expnt = Mid(bstr, 2, 8)
    e = b2d(expnt) - 127
    mntss = Right(bstr, 23)
    f = b2d(mntss)
    f = (f * 2 ^ -23) / 10 ^ -Len(f)
    i = InStr(1, f, ".")
    If i > 0 Then f = Left(f, i - 1)
    f = 1 * ("0." & Trim(Str(f))) + 1
    i3e2d = s * 2 ^ e * f
End Function

6. Open a file of (as) binary data, read a byte (at a time) as a HEX string:
[note (7-May-08): Thanks to Ken Sailor for finding an error. I had used AscB to read a byte as a number. It sometimes fails. It should be Asc]
Code: 
Open [red]filename[/red] For Binary As #1
     . . .
a1 = [red]Asc[/red](Input(1, #1))
h1 = Hex(a1)
If Len(h1) < 2 Then
  h1 = "0" & h1
End If
     . . . 
close #1

7. I like to write out binary data as both ASCII HEX and binary:
Code: 
Open [red]filename[/red] & ".asc" For Output As #1
Open [red]filename[/red] & ".bin" For Binary As #2
      . . . 
'for example, building a hex string from cells
    For rw = 2 To ActiveSheet.UsedRange.Rows.Count
        If (Cells(rw, 2) = "") Then Exit For
        wrd = Cells(rw, 5) & Cells(rw, 6) & Cells(rw, 7) _
              & Cells(rw, 8) & "00000"
        Print #1, wrd
        GoSub bin_out
    Next
    Close #1
    Close #2
    Exit Sub
bin_out:
        wrdlen = Len(wrd)
        For bix = 1 To wrdlen - 1 Step 2
            bnum = Mid(wrd, bix, 2)
            bnum2 = b2d(h2b(bnum))
            uvar$ = Chr(bnum2)
            Put #2, , uvar$
        Next
        Return

8. Two's Complement representation of negative integers
input HEX string (hs), return a Long:
Code: 
Function twoscomp(hs)
    bs = h2b(hs)
    If Left(bs, 1) = "1" Then
        bcs = Replace(bs, "1", "q")
        bcs = Replace(bs, "0", "1")
        bcs = Replace(bs, "q", "0")
        twoscomp = -1 * (CLng("&H" & b2h(bs)) + 1)
    Else
        twoscomp = CLng("&H" & hs)
    End If
End Function
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