{******************************************************************************}
{** A Base64 encoding unit ****************************************************}
{******************************************************************************}
{** Written by David Barton (davebarton@bigfoot.com) **************************}
{** http://www.scramdisk.clara.net/ *******************************************}
{******************************************************************************}
unit Base64;

interface
uses
  Sysutils;

{ Base64 encode and decode a string }
function B64Encode(const S: string): string;
function B64Decode(const S: string): string;

{******************************************************************************}
{******************************************************************************}
implementation

const
  B64Table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

function B64Encode;
var
  i: integer;
  InBuf: array[0..2] of byte;
  OutBuf: array[0..3] of char;
begin
  SetLength(Result, ((Length(S) + 2) div 3) * 4);
  for i := 1 to ((Length(S) + 2) div 3) do
  begin
    if Length(S) < (i * 3) then
      Move(S[(i - 1) * 3 + 1], InBuf, Length(S) - (i - 1) * 3)
    else
      Move(S[(i - 1) * 3 + 1], InBuf, 3);
    OutBuf[0] := B64Table[((InBuf[0] and $FC) shr 2) + 1];
    OutBuf[1] := B64Table[(((InBuf[0] and $03) shl 4) or ((InBuf[1] and $F0) shr 4)) + 1];
    OutBuf[2] := B64Table[(((InBuf[1] and $0F) shl 2) or ((InBuf[2] and $C0) shr 6)) + 1];
    OutBuf[3] := B64Table[(InBuf[2] and $3F) + 1];
    Move(OutBuf, Result[(i - 1) * 4 + 1], 4);
  end;
  if (Length(S) mod 3) = 1 then
  begin
    Result[Length(Result) - 1] := '=';
    Result[Length(Result)] := '=';
  end
  else if (Length(S) mod 3) = 2 then
    Result[Length(Result)] := '=';
end;

function B64Decode;
var
  i: integer;
  InBuf: array[0..3] of byte;
  OutBuf: array[0..2] of byte;
begin
  if (Length(S) mod 4) <> 0 then
    raise Exception.Create('Base64: Incorrect string format');
  SetLength(Result, ((Length(S) div 4) - 1) * 3);
  for i := 1 to ((Length(S) div 4) - 1) do
  begin
    Move(S[(i - 1) * 4 + 1], InBuf, 4);
    if (InBuf[0] > 64) and (InBuf[0] < 91) then
      Dec(InBuf[0], 65)
    else if (InBuf[0] > 96) and (InBuf[0] < 123) then
      Dec(InBuf[0], 71)
    else if (InBuf[0] > 47) and (InBuf[0] < 58) then
      Inc(InBuf[0], 4)
    else if InBuf[0] = 43 then
      InBuf[0] := 62
    else
      InBuf[0] := 63;
    if (InBuf[1] > 64) and (InBuf[1] < 91) then
      Dec(InBuf[1], 65)
    else if (InBuf[1] > 96) and (InBuf[1] < 123) then
      Dec(InBuf[1], 71)
    else if (InBuf[1] > 47) and (InBuf[1] < 58) then
      Inc(InBuf[1], 4)
    else if InBuf[1] = 43 then
      InBuf[1] := 62
    else
      InBuf[1] := 63;
    if (InBuf[2] > 64) and (InBuf[2] < 91) then
      Dec(InBuf[2], 65)
    else if (InBuf[2] > 96) and (InBuf[2] < 123) then
      Dec(InBuf[2], 71)
    else if (InBuf[2] > 47) and (InBuf[2] < 58) then
      Inc(InBuf[2], 4)
    else if InBuf[2] = 43 then
      InBuf[2] := 62
    else
      InBuf[2] := 63;
    if (InBuf[3] > 64) and (InBuf[3] < 91) then
      Dec(InBuf[3], 65)
    else if (InBuf[3] > 96) and (InBuf[3] < 123) then
      Dec(InBuf[3], 71)
    else if (InBuf[3] > 47) and (InBuf[3] < 58) then
      Inc(InBuf[3], 4)
    else if InBuf[3] = 43 then
      InBuf[3] := 62
    else
      InBuf[3] := 63;
    OutBuf[0] := (InBuf[0] shl 2) or ((InBuf[1] shr 4) and $03);
    OutBuf[1] := (InBuf[1] shl 4) or ((InBuf[2] shr 2) and $0F);
    OutBuf[2] := (InBuf[2] shl 6) or (InBuf[3] and $3F);
    Move(OutBuf, Result[(i - 1) * 3 + 1], 3);
  end;
  if Length(S) <> 0 then
  begin
    Move(S[Length(S) - 3], InBuf, 4);
    if InBuf[2] = 61 then
    begin
      if (InBuf[0] > 64) and (InBuf[0] < 91) then
        Dec(InBuf[0], 65)
      else if (InBuf[0] > 96) and (InBuf[0] < 123) then
        Dec(InBuf[0], 71)
      else if (InBuf[0] > 47) and (InBuf[0] < 58) then
        Inc(InBuf[0], 4)
      else if InBuf[0] = 43 then
        InBuf[0] := 62
      else
        InBuf[0] := 63;
      if (InBuf[1] > 64) and (InBuf[1] < 91) then
        Dec(InBuf[1], 65)
      else if (InBuf[1] > 96) and (InBuf[1] < 123) then
        Dec(InBuf[1], 71)
      else if (InBuf[1] > 47) and (InBuf[1] < 58) then
        Inc(InBuf[1], 4)
      else if InBuf[1] = 43 then
        InBuf[1] := 62
      else
        InBuf[1] := 63;
      OutBuf[0] := (InBuf[0] shl 2) or ((InBuf[1] shr 4) and $03);
      Result := Result + char(OutBuf[0]);
    end
    else if InBuf[3] = 61 then
    begin
      if (InBuf[0] > 64) and (InBuf[0] < 91) then
        Dec(InBuf[0], 65)
      else if (InBuf[0] > 96) and (InBuf[0] < 123) then
        Dec(InBuf[0], 71)
      else if (InBuf[0] > 47) and (InBuf[0] < 58) then
        Inc(InBuf[0], 4)
      else if InBuf[0] = 43 then
        InBuf[0] := 62
      else
        InBuf[0] := 63;
      if (InBuf[1] > 64) and (InBuf[1] < 91) then
        Dec(InBuf[1], 65)
      else if (InBuf[1] > 96) and (InBuf[1] < 123) then
        Dec(InBuf[1], 71)
      else if (InBuf[1] > 47) and (InBuf[1] < 58) then
        Inc(InBuf[1], 4)
      else if InBuf[1] = 43 then
        InBuf[1] := 62
      else
        InBuf[1] := 63;
      if (InBuf[2] > 64) and (InBuf[2] < 91) then
        Dec(InBuf[2], 65)
      else if (InBuf[2] > 96) and (InBuf[2] < 123) then
        Dec(InBuf[2], 71)
      else if (InBuf[2] > 47) and (InBuf[2] < 58) then
        Inc(InBuf[2], 4)
      else if InBuf[2] = 43 then
        InBuf[2] := 62
      else
        InBuf[2] := 63;
      OutBuf[0] := (InBuf[0] shl 2) or ((InBuf[1] shr 4) and $03);
      OutBuf[1] := (InBuf[1] shl 4) or ((InBuf[2] shr 2) and $0F);
      Result := Result + char(OutBuf[0]) + char(OutBuf[1]);
    end
    else
    begin
      if (InBuf[0] > 64) and (InBuf[0] < 91) then
        Dec(InBuf[0], 65)
      else if (InBuf[0] > 96) and (InBuf[0] < 123) then
        Dec(InBuf[0], 71)
      else if (InBuf[0] > 47) and (InBuf[0] < 58) then
        Inc(InBuf[0], 4)
      else if InBuf[0] = 43 then
        InBuf[0] := 62
      else
        InBuf[0] := 63;
      if (InBuf[1] > 64) and (InBuf[1] < 91) then
        Dec(InBuf[1], 65)
      else if (InBuf[1] > 96) and (InBuf[1] < 123) then
        Dec(InBuf[1], 71)
      else if (InBuf[1] > 47) and (InBuf[1] < 58) then
        Inc(InBuf[1], 4)
      else if InBuf[1] = 43 then
        InBuf[1] := 62
      else
        InBuf[1] := 63;
      if (InBuf[2] > 64) and (InBuf[2] < 91) then
        Dec(InBuf[2], 65)
      else if (InBuf[2] > 96) and (InBuf[2] < 123) then
        Dec(InBuf[2], 71)
      else if (InBuf[2] > 47) and (InBuf[2] < 58) then
        Inc(InBuf[2], 4)
      else if InBuf[2] = 43 then
        InBuf[2] := 62
      else
        InBuf[2] := 63;
      if (InBuf[3] > 64) and (InBuf[3] < 91) then
        Dec(InBuf[3], 65)
      else if (InBuf[3] > 96) and (InBuf[3] < 123) then
        Dec(InBuf[3], 71)
      else if (InBuf[3] > 47) and (InBuf[3] < 58) then
        Inc(InBuf[3], 4)
      else if InBuf[3] = 43 then
        InBuf[3] := 62
      else
        InBuf[3] := 63;
      OutBuf[0] := (InBuf[0] shl 2) or ((InBuf[1] shr 4) and $03);
      OutBuf[1] := (InBuf[1] shl 4) or ((InBuf[2] shr 2) and $0F);
      OutBuf[2] := (InBuf[2] shl 6) or (InBuf[3] and $3F);
      Result := Result + Char(OutBuf[0]) + Char(OutBuf[1]) + Char(OutBuf[2]);
    end;
  end;
end;

end.