Const sBASE_64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
' ---------------------------------------
Function Base64decode(ByVal asContents)
    Dim lsResult
    Dim lnPosition
    Dim lsGroup64, lsGroupBinary
    Dim Char1, Char2, Char3, Char4
    Dim Byte1, Byte2, Byte3
    If Len(asContents) Mod 4 > 0 Then asContents = asContents & String(4 - (Len(asContents) Mod 4), " ")
    lsResult = ""
    
    For lnPosition = 1 To Len(asContents) Step 4
        lsGroupBinary = ""
        lsGroup64 = Mid(asContents, lnPosition, 4)
        Char1 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 1, 1)) - 1
        Char2 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 2, 1)) - 1
        Char3 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 3, 1)) - 1
        Char4 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 4, 1)) - 1
        Byte1 = Chr(((Char2 And 48)  16) Or (Char1 * 4) And &HFF)
        Byte2 = lsGroupBinary & Chr(((Char3 And 60)  4) Or (Char2 * 16) And &HFF)
        Byte3 = Chr((((Char3 And 3) * 64) And &HFF) Or (Char4 And 63))
        lsGroupBinary = Byte1 & Byte2 & Byte3
        
        lsResult = lsResult + lsGroupBinary
    Next
    Base64decode = lsResult
End Function
' --------------------------------------

Function Base64encode(ByVal asContents)
    Dim lnPosition
    Dim lsResult
    Dim Char1
    Dim Char2
    Dim Char3
    Dim Char4
    Dim Byte1
    Dim Byte2
    Dim Byte3
    Dim SaveBits1
    Dim SaveBits2
    Dim lsGroupBinary
    Dim lsGroup64
    
    If Len(asContents) Mod 3 > 0 Then asContents = asContents & String(3 - (Len(asContents) Mod 3), " ")
    lsResult = ""
    
    For lnPosition = 1 To Len(asContents) Step 3
        lsGroup64 = ""
        lsGroupBinary = Mid(asContents, lnPosition, 3)

        Byte1 = Asc(Mid(lsGroupBinary, 1, 1)): SaveBits1 = Byte1 And 3
        Byte2 = Asc(Mid(lsGroupBinary, 2, 1)): SaveBits2 = Byte2 And 15
        Byte3 = Asc(Mid(lsGroupBinary, 3, 1))

        Char1 = Mid(sBASE_64_CHARACTERS, ((Byte1 And 252)  4) + 1, 1)
        Char2 = Mid(sBASE_64_CHARACTERS, (((Byte2 And 240)  16) Or (SaveBits1 * 16) And &HFF) + 1, 1)
        Char3 = Mid(sBASE_64_CHARACTERS, (((Byte3 And 192)  64) Or (SaveBits2 * 4) And &HFF) + 1, 1)
        Char4 = Mid(sBASE_64_CHARACTERS, (Byte3 And 63) + 1, 1)
        lsGroup64 = Char1 & Char2 & Char3 & Char4
        
        lsResult = lsResult + lsGroup64
    Next
    
    Base64encode = lsResult
End Function