Автор: Евгений

const

 Base64Table =
 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

function Base64Decode(cStr: string): string;
var
 ResStr: string;

 DecStr: string;
 RecodeLine: array[1..76] of byte;
 f1, f2: word;
 l: integer;
begin
 l := length(cStr);
 ResStr := '';
 for f1 := 1 to l do
 if cStr[f1] = '=' then
 RecodeLine[f1] := 0
 else
 RecodeLine[f1] := pos(cStr[f1], Base64Table) - 1;
 f1 := 1;
 while f1 < length(cStr) do
 begin
 DecStr := chr(byte(RecodeLine[f1] shl 2) + RecodeLine[f1 + 1] shr 4) +
 chr(byte(RecodeLine[f1 + 1] shl 4) + RecodeLine[f1 + 2] shr 2) +
 chr(byte(RecodeLine[f1 + 2] shl 6) + RecodeLine[f1 + 3]);
 ResStr := ResStr + DecStr;
 inc(f1, 4);
 end;
 Base64Decode := ResStr;
end;