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[VBA]Base64编码和Base64解码

March 26th, 2019 No comments

VBA实现Base64编码和Base64解码,用于处理加密的URL非常方便。

VBA Base64 编码/加密函数:

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'VBA Base64 编码/加密函数:
Function Base64Encode(StrA As String) As String                                  'Base64 编码
    On Error GoTo over                                                          '排错
    Dim buf() As Byte, length As Long, mods As Long
    Dim Str() As Byte
    Dim i, kk As Integer
    kk = Len(StrA) - 1
    ReDim Str(kk)
    For i = 0 To kk
        Str(i) = Asc(Mid(StrA, i + 1, 1))
    Next i
    Const B64_CHAR_DICT = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
    mods = (UBound(Str) + 1) Mod 3   '除以3的余数
    length = UBound(Str) + 1 - mods
    ReDim buf(length / 3 * 4 + IIf(mods <> 0, 4, 0) - 1)
    For i = 0 To length - 1 Step 3
        buf(i / 3 * 4) = (Str(i) And &HFC) / &H4
        buf(i / 3 * 4 + 1) = (Str(i) And &H3) * &H10 + (Str(i + 1) And &HF0) / &H10
        buf(i / 3 * 4 + 2) = (Str(i + 1) And &HF) * &H4 + (Str(i + 2) And &HC0) / &H40
        buf(i / 3 * 4 + 3) = Str(i + 2) And &H3F
    Next
    If mods = 1 Then
        buf(length / 3 * 4) = (Str(length) And &HFC) / &H4
        buf(length / 3 * 4 + 1) = (Str(length) And &H3) * &H10
        buf(length / 3 * 4 + 2) = 64
        buf(length / 3 * 4 + 3) = 64
    ElseIf mods = 2 Then
        buf(length / 3 * 4) = (Str(length) And &HFC) / &H4
        buf(length / 3 * 4 + 1) = (Str(length) And &H3) * &H10 + (Str(length + 1) And &HF0) / &H10
        buf(length / 3 * 4 + 2) = (Str(length + 1) And &HF) * &H4
        buf(length / 3 * 4 + 3) = 64
    End If
    For i = 0 To UBound(buf)
        Base64Encode = Base64Encode + Mid(B64_CHAR_DICT, buf(i) + 1, 1)
    Next
over:
End Function

VBA Base64 解码/解密函数:

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'VBA Base64 解码/解密函数:
Function Base64Decode(B64 As String) As String                                  'Base64 解码
    On Error GoTo over                                                          '排错
    Dim OutStr() As Byte, i As Long, j As Long
    Const B64_CHAR_DICT = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
    If InStr(1, B64, "=") <> 0 Then B64 = Left(B64, InStr(1, B64, "=") - 1)     '判断Base64真实长度,除去补位
    Dim kk, length As Long, mods As Long
    mods = Len(B64) Mod 4
    length = Len(B64) - mods
    ReDim OutStr(length / 4 * 3 - 1 + Switch(mods = 0, 0, mods = 2, 1, mods = 3, 2))
    For i = 1 To length Step 4
        Dim buf(3) As Byte
        For j = 0 To 3
            buf(j) = InStr(1, B64_CHAR_DICT, Mid(B64, i + j, 1)) - 1            '根据字符的位置取得索引值
        Next
        OutStr((i - 1) / 4 * 3) = buf(0) * &H4 + (buf(1) And &H30) / &H10
        OutStr((i - 1) / 4 * 3 + 1) = (buf(1) And &HF) * &H10 + (buf(2) And &H3C) / &H4
        OutStr((i - 1) / 4 * 3 + 2) = (buf(2) And &H3) * &H40 + buf(3)
    Next
    If mods = 2 Then
        OutStr(length / 4 * 3) = (InStr(1, B64_CHAR_DICT, Mid(B64, length + 1, 1)) - 1) * &H4 + ((InStr(1, B64_CHAR_DICT, Mid(B64, length + 2, 1)) - 1) And &H30) / 16
    ElseIf mods = 3 Then
        OutStr(length / 4 * 3) = (InStr(1, B64_CHAR_DICT, Mid(B64, length + 1, 1)) - 1) * &H4 + ((InStr(1, B64_CHAR_DICT, Mid(B64, length + 2, 1)) - 1) And &H30) / 16
        OutStr(length / 4 * 3 + 1) = ((InStr(1, B64_CHAR_DICT, Mid(B64, length + 2, 1)) - 1) And &HF) * &H10 + ((InStr(1, B64_CHAR_DICT, Mid(B64, length + 3, 1)) - 1) And &H3C) / &H4
    End If
    For i = 0 To UBound(OutStr)
        Base64Decode = Base64Decode & Chr(OutStr(i))
    Next i                                                       '读取解码结果
over:
End Function

参考:http://club.excelhome.net/forum.php?mod=viewthread&tid=1239744&ordertype=1

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