牧羊人的開發歷程

Public Function Base64Encode(InStr1 As String) As String
    Dim mInByte(3) As Byte, mOutByte(4) As Byte
    Dim myByte As Byte
    Dim i As Integer, LenArray As Integer, J As Integer
    Dim myBArray() As Byte
    Dim OutStr1 As String
    
    myBArray() = StrConv(InStr1, vbFromUnicode)
    LenArray = UBound(myBArray) + 1
    For i = 0 To LenArray Step 3
        If LenArray - i = 0 Then
            Exit For
        End If
        If LenArray - i = 2 Then
            mInByte(0) = myBArray(i)
            mInByte(1) = myBArray(i + 1)
            Base64EncodeByte mInByte, mOutByte, 2
        ElseIf LenArray - i = 1 Then
            mInByte(0) = myBArray(i)
            Base64EncodeByte mInByte, mOutByte, 1
        Else
            mInByte(0) = myBArray(i)
            mInByte(1) = myBArray(i + 1)
            mInByte(2) = myBArray(i + 2)
            Base64EncodeByte mInByte, mOutByte, 3
        End If
        For J = 0 To 3
            OutStr1 = OutStr1 & Chr(mOutByte(J))
        Next J
    Next i
    Base64Encode = OutStr1
End Function

Public Function Base64Decode(InStr1 As String) As String
   Dim mInByte(4) As Byte, mOutByte(3) As Byte
   Dim i As Integer, LenArray As Integer, J As Integer
   Dim myBArray() As Byte
   Dim OutStr1 As String
   Dim tmpArray() As Byte
   myBArray() = StrConv(InStr1, vbFromUnicode)
   LenArray = UBound(myBArray)
   ReDim tmpArray(((LenArray + 1) / 4) * 3)
    J = 0
    
    For i = 0 To LenArray Step 4
       If LenArray - i = 0 Then
           Exit For
Else
            mInByte(0) = myBArray(i)
            mInByte(1) = myBArray(i + 1)
            mInByte(2) = myBArray(i + 2)
            mInByte(3) = myBArray(i + 3)
            Base64DecodeByte mInByte, mOutByte, 4
        End If
        tmpArray(J * 3) = mOutByte(0)
        tmpArray(J * 3 + 1) = mOutByte(1)
        tmpArray(J * 3 + 2) = mOutByte(2)
        J = J + 1
    Next i
    Base64Decode = BinaryToString(tmpArray)
End Function

Private Sub Base64EncodeByte(mInByte() As Byte, mOutByte() As Byte, Num As Integer)
   Dim tByte As Byte
   Dim i As Integer
   If Num = 1 Then
       mInByte(1) = 0
       mInByte(2) = 0
   ElseIf Num = 2 Then
       mInByte(2) = 0
   End If
   tByte = mInByte(0) And &HFC
   mOutByte(0) = tByte / 4
   tByte = ((mInByte(0) And &H3) * 16) + (mInByte(1) And &HF0) / 16
   mOutByte(1) = tByte
   tByte = ((mInByte(1) And &HF) * 4) + ((mInByte(2) And &HC0) / 64)
   mOutByte(2) = tByte
   tByte = (mInByte(2) And &H3F)
   mOutByte(3) = tByte
   For i = 0 To 3
       If mOutByte(i) >= 0 And mOutByte(i) <= 25 Then
           mOutByte(i) = mOutByte(i) + Asc("A")
       ElseIf mOutByte(i) >= 26 And mOutByte(i) <= 51 Then
           mOutByte(i) = mOutByte(i) - 26 + Asc("a")
       ElseIf mOutByte(i) >= 52 And mOutByte(i) <= 61 Then
           mOutByte(i) = mOutByte(i) - 52 + Asc("0")
       ElseIf mOutByte(i) = 62 Then
           mOutByte(i) = Asc("+")
       Else
           mOutByte(i) = Asc("/")
       End If
   Next i
   If Num = 1 Then
       mOutByte(2) = Asc("=")
       mOutByte(3) = Asc("=")
   ElseIf Num = 2 Then
       mOutByte(3) = Asc("=")
   End If
End Sub

Private Sub Base64DecodeByte(mInByte() As Byte, mOutByte() As Byte, ByteNum As Integer)
    Dim tByte As Byte
    Dim i As Integer
    ByteNum = 0
    For i = 0 To 3
        If mInByte(i) >= Asc("A") And mInByte(i) <= Asc("Z") Then
            mInByte(i) = mInByte(i) - Asc("A")
        ElseIf mInByte(i) >= Asc("a") And mInByte(i) <= Asc("z") Then
            mInByte(i) = mInByte(i) - Asc("a") + 26
        ElseIf mInByte(i) >= Asc("0") And mInByte(i) <= Asc("9") Then
            mInByte(i) = mInByte(i) - Asc("0") + 52
        ElseIf mInByte(i) = Asc("+") Then
            mInByte(i) = 62
        ElseIf mInByte(i) = Asc("/") Then
            mInByte(i) = 63
        Else '"="
            ByteNum = ByteNum + 1
            mInByte(i) = 0
        End If
    Next i
    '取前六位
    tByte = (mInByte(0) And &H3F) * 4 + (mInByte(1) And &H30) / 16
    '0的六位和1的前兩位
    mOutByte(0) = tByte
    tByte = (mInByte(1) And &HF) * 16 + (mInByte(2) And &H3C) / 4
    '1的後四位和2的前四位
    mOutByte(1) = tByte
    tByte = (mInByte(2) And &H3) * 64 + (mInByte(3) And &H3F)
    mOutByte(2) = tByte
    '2的後兩位和3的六位
End Sub

Private Function BinaryToString(ByVal BinaryStr As Variant) As String '二進制轉換為字符串
  Dim lnglen As Long
  Dim tmpBin As Variant
  Dim strC As String
  Dim skipflag As Long
  Dim i As Long
  skipflag = 0
  strC = ""
  
  If Not IsNull(BinaryStr) Then
      lnglen = LenB(BinaryStr)
      For i = 1 To lnglen
          If skipflag = 0 Then
            tmpBin = MidB(BinaryStr, i, 1)
            If AscB(tmpBin) > 127 Then
                strC = strC & Chr(AscW(MidB(BinaryStr, i + 1, 1) & tmpBin))
                skipflag = 1
            Else
                strC = strC & Chr(AscB(tmpBin))
            End If
          Else
            skipflag = 0
          End If
      Next
    End If
    BinaryToString = strC
End Function

Private Function StringToBinary(ByVal VarString As String) As Variant '字符串轉成二進制
  Dim strBin As Variant
  Dim varchar As Variant
  Dim varasc As Long
  Dim varlow, varhigh
  Dim i As Long
  strBin = ""
  
  For i = 1 To Len(VarString)
      varchar = Mid(VarString, i, 1)
      varasc = Asc(varchar)
      If varasc < 0 Then
          varasc = varasc + 65535
      End If
      If varasc > 255 Then
          varlow = Left(Hex(Asc(varchar)), 2)
          varhigh = Right(Hex(Asc(varchar)), 2)
          strBin = strBin & ChrB("&H" & varlow) & ChrB("&H" & varhigh)
      Else
          strBin = strBin & ChrB(AscB(varchar))
      End If
  Next
  StringToBinary = strBin
End Function