VB6 - Binary (string of bits) to Long

[dilettante]

You've probably seen several of these, but this one avoids the performance trap of using exponentiation. As far as I know it works without quirks or bugs:

Option Explicit

Function Bits2Long(ByVal Bits As String) As Long
    Dim L As Long, Bits32 As Long, I As Long
    
    L = Len(Bits)
    If 1 > L Or L > 32 Or Bits Like "*[!01]*" Then Err.Raise 5
    If L = 32 Then Bits32 = 1
    For I = Bits32 + 1 To L
        Bits2Long = 2 * Bits2Long + (AscW(Mid$(Bits, I, 1)) - 48)
    Next
    If Bits32 And AscW(Bits) = 49 Then Bits2Long = Bits2Long Or &H80000000
End Function

Function Bits2LongV2(ByVal Bits As String) As Long
    'Stripped down, no error checking, only 1- to 31-bit argument:
    Dim I As Long
    
    For I = 1 To Len(Bits)
        Bits2LongV2 = 2 * Bits2LongV2 + (AscW(Mid$(Bits, I, 1)) - 48)
    Next
End Function

Private Sub Try(ByVal Bits As String)
    On Error Resume Next
    Print Hex$(Bits2Long(Bits)); Tab(16); Bits2Long(Bits); Tab(32); Bits
    If Err Then
        Print "Invalid parameter:"; Tab(32); Bits
    End If
End Sub

Private Sub Try2(ByVal Bits As String)
    Print Hex$(Bits2LongV2(Bits)); Tab(16); Bits2LongV2(Bits); Tab(32); Bits
End Sub

Private Sub Form_Load()
    AutoRedraw = True
    
    Try "11111111111111111111111111111111"
    Try "01111111111111111111111111111111"
    Try "0"
    Try "2"
    Try ""
    Try "111111111111111111111111111111111"
    Try "10101010"
    Try2 "10101010"
End Sub