function Decode(const S: AnsiString): AnsiString;
const
 Map: array[Char] of Byte = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, 0, 0, 0, 63, 52, 53,
 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2,
 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30,
 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,
 46, 47, 48, 49, 50, 51, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 0);
var
 I: LongInt;
begin
 case Length(S) of
 2:
 begin
 I := Map[S[1]] + (Map[S[2]] shl 6);
 SetLength(Result, 1);
 Move(I, Result[1], Length(Result))
 end;
 3:
 begin
 I := Map[S[1]] + (Map[S[2]] shl 6) + (Map[S[3]] shl 12);
 SetLength(Result, 2);
 Move(I, Result[1], Length(Result))
 end;
 4:
 begin
 I := Map[S[1]] + (Map[S[2]] shl 6) + (Map[S[3]] shl 12) +
 (Map[S[4]] shl 18);
 SetLength(Result, 3);
 Move(I, Result[1], Length(Result))
 end
 end
end;

function Encode(const S: AnsiString): AnsiString;
const
 Map: array[0..63] of Char = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' +
 'abcdefghijklmnopqrstuvwxyz0123456789+/';
var
 I: LongInt;
begin
 I := 0;
 Move(S[1], I, Length(S));
 case Length(S) of
 1:
 Result := Map[I mod 64] + Map[(I shr 6) mod 64];
 2:
 Result := Map[I mod 64] + Map[(I shr 6) mod 64] +
 Map[(I shr 12) mod 64];
 3:
 Result := Map[I mod 64] + Map[(I shr 6) mod 64] +
 Map[(I shr 12) mod 64] + Map[(I shr 18) mod 64]
 end
end;