Title: How to encode / decode Base64 string
const
Codes64 = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/';
function Encode64(S: string): string;
var
i: Integer;
a: Integer;
x: Integer;
b: Integer;
begin
Result := '';
a := 0;
b := 0;
for i := 1 to Length(s) do
begin
x := Ord(s[i]);
b := b * 256 + x;
a := a + 8;
while a = 6 do
begin
a := a - 6;
x := b div (1 shl a);
b := b mod (1 shl a);
Result := Result + Codes64[x + 1];
end;
end;
if a 0 then
begin
x := b shl (6 - a);
Result := Result + Codes64[x + 1];
end;
end;
function Decode64(S: string): string;
var
i: Integer;
a: Integer;
x: Integer;
b: Integer;
begin
Result := '';
a := 0;
b := 0;
for i := 1 to Length(s) do
begin
x := Pos(s[i], codes64) - 1;
if x = 0 then
begin
b := b * 64 + x;
a := a + 6;
if a = 8 then
begin
a := a - 8;
x := b shr a;
b := b mod (1 shl a);
x := x mod 256;
Result := Result + chr(x);
end;
end
else
Exit;
end;
end;