dahual

主要还是编码的问题。
通过解决这个问题，让我觉得字节是最完美的。

'参考链接：
'http://maclife.net/tools/base64/
'http://blog.csdn.net/zym_123456/archive/2008/03/30/2230695.aspx
Option Explicit

MsgBox Base64ToText_Utf8Encode("5om55aSE55CG5LmL5a62")

'Base64ToText_utf8Encode
Function Base64ToText_Utf8Encode(s)
	Dim i
	Dim bArr,bRet
	ReDim bArr(Len(s)-1)
	
	For i=1 To Len(s)
		bArr(i-1)=Asc(Mid(s,i,1))
	Next
	bRet=Base64_Decode(bArr)
	Base64ToText_utf8Encode=Utf8ToUnicode(bRet)
End Function

'Utf8ToUnicode
Function Utf8ToUnicode(src)
	Dim IsAsc
	Dim utfLen
	utfLen = -1
	
	On Error Resume Next
	utfLen = UBound(src)-LBound(src)+1
	If utfLen = -1 Then Exit Function
	On Error GoTo 0
	
	Dim i,j,k,N
	Dim B,cnt
	ReDim Buf(utfLen)
	i = 1
	j = 0
	Do While i <= utfLen
		B = src(i-1)
		If (B And &HFC) = &HFC Then
			cnt = 6
		ElseIf (B And &HF8) = &HF8 Then
			cnt = 5
		ElseIf (B And &HF0) = &HF0 Then
			cnt = 4
		ElseIf (B And &HE0) = &HE0 Then
			cnt = 3
		ElseIf (B And &HC0) = &HC0 Then
			cnt = 2
		Else
			cnt = 1
		End If
		If i + cnt - 1 > utfLen Then
			Buf(j) = "?"
			Exit Do
		End If
		Select Case cnt
			Case 2
				N = B And &H1F
			Case 3
				N = B And &HF
			Case 4
				N = B And &H7
			Case 5
				N = B And &H3
			Case 6
				N = B And &H1
			Case Else
				Buf(j) = Chr(B)
				IsAsc=True
		End Select
		If IsAsc=False Then
			For k = 1 To cnt - 1
				B = src(i+k-1)
				N = N * &H40 + (B And &H3F)
			Next
			Buf(j) = ChrW(N)
		End If
		i = i + cnt
		j = j + 1
		IsAsc=False
	Loop
	Utf8ToUnicode = Join(Buf, "")
End Function

'Base64解码函数
Public Function Base64_Decode(bytInText)
    Dim Base64DecodeTable(122)
    Dim lngInTextLen, i
    Dim bytDecode, lngDecodeLen
    
    Base64_Decode = Chr(0)  '初始化函数返回值
    
    If LBound(bytInText) <> 0 Then Exit Function  'bytInText数组下标不从零开始则出错返回
    
    lngInTextLen = UBound(bytInText) - LBound(bytInText) + 1  '计算bytInText数组长度
    If lngInTextLen Mod 4 <> 0 Then Exit Function  '输入编码不是4的倍数则出错返回
    
    For i = 1 To 122  '初始化Base64解码表
        Select Case True
        Case i=43  '+
            Base64DecodeTable(i) = 62
        Case i=47  '/
            Base64DecodeTable(i) = 63
        Case i>=48 And i<=57  '0 - 9
            Base64DecodeTable(i) = 52 + (i - 48)
        Case i>=65 And i<=90  'A - Z
            Base64DecodeTable(i) = 0 + (i - 65)
        Case i>=97 And i<=122  'a - z
            Base64DecodeTable(i) = 26 + (i - 97)
        Case Else
            Base64DecodeTable(i) = 255
        End Select
    Next
    lngDecodeLen = lngInTextLen / 4 * 3  '求解码后的最大长度
    ReDim bytDecode(lngDecodeLen - 1)  '重新定义解码缓冲区
    'MsgBox "解码后的最大长度为：" & lngDecodeLen
    
    lngDecodeLen = 0  '初始化解码长度
    
    For i = 0 To lngInTextLen - 1 Step 4
        bytDecode(lngDecodeLen) = (Base64DecodeTable(bytInText(i)) * (2 ^ 2)) Or ((Base64DecodeTable(bytInText(i + 1)) And &H30) \ (2 ^ 4))
        bytDecode(lngDecodeLen + 1) = ((Base64DecodeTable(bytInText(i + 1)) And &HF) * (2 ^ 4)) Or ((Base64DecodeTable(bytInText(i + 2)) And &H3C) \ (2 ^ 2))
        bytDecode(lngDecodeLen + 2) = ((Base64DecodeTable(bytInText(i + 2)) And &H3) * (2 ^ 6)) Or Base64DecodeTable(bytInText(i + 3))
        lngDecodeLen = lngDecodeLen + 3
    Next
    
    If bytInText(lngInTextLen - 1) = &H3D Then  '判断最后两个字节的情况,求解码后的实际长度
        If bytInText(lngInTextLen - 2) = &H3D Then
            lngDecodeLen = lngDecodeLen - 2  '最后两个字节为"="
        Else
            lngDecodeLen = lngDecodeLen - 1  '最后一个字节为"="
        End If
        bytDecode(lngDecodeLen) = 0  '在实际长度的后一个字节放个结束符
    End If
    'MsgBox "解码后的实际长度为：" & lngDecodeLen
    
    Base64_Decode = bytDecode
End Function
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