[ASP] BASE64 인코딩(encoding)/디코딩(decoding)

<%@Language="VBSCRIPT" CODEPAGE="949"%>

<%

Response.CharSet = "EUC-KR"

Session.CodePage = 949

Dim Str,Flag : Str = Request("str")

%>

<form method="get" action="">

<input type="text" name="str" value="<%=Str%>">

<input type="submit">

</form>

<%

Response.Write "STRING : " & Str & "<BR>"

Response.Write "ENCODE : " & BASE64_ENCODE(Str) & "<BR>"

Response.Write "DECODE : " & BASE64_DECODE(BASE64_ENCODE(Str)) & "<BR>"

Function BASE64_KEY(ByVal Num,ByVal Flag)

Const Key = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

If UCase(FLAG) = "EN" Then 

BASE64_KEY = Mid(Key,Num+1,1)

ElseIf UCase(FLAG) = "DE" Then 

BASE64_KEY = InStr(Key,Num)-1

End If

End Function

Function BASE64_ENCODE(ByVal eSTR)

Dim BinStr, Tmp, Padding

ReDim ArrayStr(Len(eSTR))

For i = 1 To Len(eStr)

ArrayStr(i) = Int("&H" & Right("0000" & Hex(Asc(Mid(eStr,i,1))),4))

Tmp = Empty

Do While ArrayStr(i) > 0

        Tmp = Tmp & ArrayStr(i) Mod 2

        ArrayStr(i) = Int(ArrayStr(i) / 2)

Loop

If Len(Tmp) > 8 Then

ArrayStr(i) = StrReverse(Tmp)

Else

ArrayStr(i) = Right("00000000" & StrReverse(Tmp),8)

End If

BinStr = BinStr & ArrayStr(i)

Next

Padding = Len(BinStr) Mod 3

ReDim ArrayStr(Round(Len(BinStr)/6-1+0.49))

For i = 0 To UBound(ArrayStr)

ArrayStr(i) = Left(BinStr,6)

If Len(BinStr) > 6 Then 

BinStr = Right(BinStr,Len(BinStr)-6)

End If

Next

If Len(ArrayStr(UBound(ArrayStr))) <> 6 Then 

ArrayStr(UBound(ArrayStr)) = Left(ArrayStr(UBound(ArrayStr)) & "000000",6)

End If

For i = 0 To UBound(ArrayStr)

BASE64_ENCODE = BASE64_ENCODE & BASE64_KEY(BinToDec(ArrayStr(i)),"EN")

Next

For i = 1 To Padding

BASE64_ENCODE =  BASE64_ENCODE & "="

Next

End Function

'2진수 -> 10진수  

Function BinToDec(strBin)  

    Dim lTot, ctr, nLen : lTot = 0

    nLen = Len(strBin)  

    For ctr = nLen - 1 To 1 Step -1  

        lTot = lTot + (2 * CInt(Mid(strBin, ctr, 1))) ^ (nLen - ctr)  

    Next  

    BinToDec = lTot + CInt(Mid(strBin, nLen, 1))  

End Function   

Function BASE64_DECODE(ByVal eStr)

Dim tmp, binStr : binStr = Empty

eStr = Replace(eStr,"=","")

ReDim ArrayStr(Len(eStr))

For i = 1 To Len(eStr)

ArrayStr(i) = Mid(eStr,i,1)

ArrayStr(i) = BASE64_KEY(ArrayStr(i),"DE")

tmp = Empty

Do While ArrayStr(i) > 0

        Tmp = Tmp & ArrayStr(i) Mod 2

        ArrayStr(i) = Int(ArrayStr(i) / 2)

Loop

binStr = binStr & Right("000000" & StrReverse(Tmp), 6)

Next

ReDim ArrayStr(Round(Len(BinStr)/8-1+0.49))

For i = 0 To UBound(ArrayStr)

ArrayStr(i) = Left(BinStr,8)

If Len(BinStr) > 8 Then 

BinStr = Right(BinStr,Len(BinStr)-8)

End If

Next

For I = 0 To UBound(ArrayStr)

If ArrayStr(i) > 0 Then 

If Asc(ArrayStr(i)) = 48 Then 

BASE64_DECODE = BASE64_DECODE & Chr(BinToDec(ArrayStr(i)))

Else

BASE64_DECODE = BASE64_DECODE & Chr(BinToDec(ArrayStr(i)&ArrayStr(i+1)))

i = i + 1

End If

End If

Next

End Function

%>