{ 64-битное декодирование файлов }
{ Arne de Bruijn }
uses dos;
var

 Base64: array[43..122] of byte;
var

 T: text;
 Chars: set of char;
 S: string;
 K, I, J: word;
 Buf: pointer;
 DShift: integer;
 F: file;
 B, B1: byte;
 Decode: array[0..63] of byte;
 Shift2: byte;
 Size, W: word;
begin
 FillChar(Base64, SizeOf(Base64), 255);
 J := 0;
 for I := 65 to 90 do
 begin
 Base64[I] := J;
 Inc(J);
 end;
 for I := 97 to 122 do
 begin
 Base64[I] := J;
 Inc(J);
 end;
 for I := 48 to 57 do
 begin
 Base64[I] := J;
 Inc(J);
 end;
 Base64[43] := J;
 Inc(J);
 Base64[47] := J;
 Inc(J);
 if ParamCount = 0 then
 begin
 WriteLn('UNBASE64  [<выходной файл>]');
 Halt(1);
 end;
 S := ParamStr(1);
 assign(T, S);
 GetMem(Buf, 32768);
 SetTextBuf(T, Buf^, 32768);
{$I-}reset(T);
{$I+}
 if IOResult <> 0 then
 begin
 WriteLn('Ошибка считывания ', S);
 Halt(1);
 end;
 if ParamCount >= 2 then
 S := ParamStr(2)
 else
 begin
 write('Расположение:');
 ReadLn(S);
 end;
 assign(F, S);
{$I-}rewrite(F, 1);
{$I+}
 if IOResult <> 0 then
 begin
 WriteLn('Ошибка создания ', S);
 Halt(1);
 end;
 while not eof(T) do
 begin
 ReadLn(T, S);
 if (S <> '') and (pos(' ', S) = 0) and (S[1] >= #43) and (S[1] <= #122) and
 (Base64[byte(S[1])] <> 255) then
 begin
 FillChar(Decode, SizeOf(Decode), 0);
 DShift := 0;
 J := 0;
 Shift2 := 1;
 Size := 255;
 B := 0;
 for I := 1 to Length(S) do
 begin
 case S[I] of
 #43..#122: B1 := Base64[Ord(S[I])];
 else
 B1 := 255;
 end;
 if B1 = 255 then
 if S[I] = '=' then
 begin
 B1 := 0;
 if Size = 255 then
 Size := J;
 end
 else
 WriteLn('Ошибка символа:', S[I], ' (', Ord(S[I]), ')');
 if DShift and 7 = 0 then
 begin
 Decode[J] := byte(B1 shl 2);
 DShift := 2;
 end
 else
 begin
 Decode[J] := Decode[J] or Hi(word(B1) shl (DShift + 2));
 Decode[J + 1] := Lo(word(B1) shl (DShift + 2));
 Inc(J);
 Inc(DShift, 2);
 end;
 end;
 if Size = 255 then
 Size := J;
 BlockWrite(F, Decode, Size);
 end;
 end;
 Close(F);
 close(T);
end.