Base64加密解密函数

答案：
<%
     OPTION EXPLICIT
     const BASE_64_MAP_INIT = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
     dim newline
     dim Base64EncMap(63)
     dim Base64DecMap(127)
     '初始化函数
     PUBLIC SUB initCodecs()
          ' 初始化变量
          newline = "<P>" & chr(13) & chr(10)
          dim max, idx
             max = len(BASE_64_MAP_INIT)
          for idx = 0 to max - 1
               Base64EncMap(idx) = mid(BASE_64_MAP_INIT, idx + 1, 1)
          next
          for idx = 0 to max - 1
               Base64DecMap(ASC(Base64EncMap(idx))) = idx
          next
     END SUB
     'Base64加密函数
     PUBLIC FUNCTION base64Encode(plain)
          if len(plain) = 0 then
               base64Encode = ""
               exit function
          end if
          dim ret, ndx, by3, first, second, third
          by3 = (len(plain) \ 3) * 3
          ndx = 1
          do while ndx <= by3
               first  = asc(mid(plain, ndx+0, 1))
               second = asc(mid(plain, ndx+1, 1))
               third  = asc(mid(plain, ndx+2, 1))
               ret = ret & Base64EncMap(  (first \ 4) AND 63 )
               ret = ret & Base64EncMap( ((first * 16) AND 48) + ((second \ 16) AND 15 ) )
               ret = ret & Base64EncMap( ((second * 4) AND 60) + ((third \ 64) AND 3 ) )
               ret = ret & Base64EncMap( third AND 63)
               ndx = ndx + 3
          loop
          if by3 < len(plain) then
               first  = asc(mid(plain, ndx+0, 1))
               ret = ret & Base64EncMap(  (first \ 4) AND 63 )
               if (len(plain) MOD 3 ) = 2 then
                    second = asc(mid(plain, ndx+1, 1))
                    ret = ret & Base64EncMap( ((first * 16) AND 48) + ((second \ 16) AND 15 ) )
                    ret = ret & Base64EncMap( ((second * 4) AND 60) )
               else
                    ret = ret & Base64EncMap( (first * 16) AND 48)
                    ret = ret '& "="
               end if
               ret = ret '& "="
          end if
          base64Encode = ret
     END FUNCTION
     'Base64解密函数
     PUBLIC FUNCTION base64Decode(scrambled)
          if len(scrambled) = 0 then
               base64Decode = ""
               exit function
          end if
          dim realLen
          realLen = len(scrambled)
          do while mid(scrambled, realLen, 1) = "="
               realLen = realLen - 1
          loop
          dim ret, ndx, by4, first, second, third, fourth
          ret = ""
          by4 = (realLen \ 4) * 4
          ndx = 1
          do while ndx <= by4
               first  = Base64DecMap(asc(mid(scrambled, ndx+0, 1)))
               second = Base64DecMap(asc(mid(scrambled, ndx+1, 1)))
               third  = Base64DecMap(asc(mid(scrambled, ndx+2, 1)))
               fourth = Base64DecMap(asc(mid(scrambled, ndx+3, 1)))
               ret = ret & chr( ((first * 4) AND 255) +   ((second \ 16) AND 3))
               ret = ret & chr( ((second * 16) AND 255) + ((third \ 4) AND 15))
               ret = ret & chr( ((third * 64) AND 255) +  (fourth AND 63))
               ndx = ndx + 4
          loop
          if ndx < realLen then
               first  = Base64DecMap(asc(mid(scrambled, ndx+0, 1)))
               second = Base64DecMap(asc(mid(scrambled, ndx+1, 1)))
   

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