/*
When developing user interfaces that support entering or modifying the user PIN, your application should prompt the user to enter between 1 and 8 ASCII characters in the range of 0
through 9.

When translating the PIN value entered by the user into data for an API call, you should convert
the input string into 4-byte BCD representation, in little-endian format (for example,
0x12345678 in binary is passed to the library as 0x78654312) before passing the PIN to a
library function.
*/
unsigned long __stdcall ChangeCode(char * OldCode,  unsigned long   OldCodeLen, unsigned char * NewCode, unsigned long NewCodeLen);

function ChangeCode(OldCode: PByte; OldCodeLen: NativeUInt; NewCode: PByte; NewCodeLen: NativeUInt): NativeUInt; stdcall;external ApiLib;

procedure ChangeUserPIN(const AOldPIN, ANewPIN: string);

  function Endian(L: Integer): Integer;
  begin
    Result := Swap(L shr 16) or (Integer(Swap(L and $ffff)) shl 16);
  end;

  function SwapInteger(i: integer): integer;
  begin    
    i := i shr 24 or i shl 24 or i and $FF00 shl 8 or i and $FF0000 shr 8;
    Result := i;
  end;

var
  a, b: Integer;
  s, t: array[0..3] of Byte;
begin

  a := StrToInt(AOldPIN);
  b := StrToInt(ANewPIN);

  PInteger(@s)^ := SwapInteger(a);
  PInteger(@t)^ := SwapInteger(b);

  CheckStatus(ChangeCode(@s, 4, @t, 4));
end;

procedure ChangeUserPIN(const AOldPIN, ANewPIN: string);

  function SwapInteger(i: integer): integer;
  begin    
    i := i shr 24 or i shl 24 or i and $FF00 shl 8 or i and $FF0000 shr 8;
    Result := i;
  end;

var
  iOldPin, iNewPin: Integer;
begin

  iOldPin := SwapInteger(StrToInt(AOldPIN));
  iNewPin := SwapInteger(StrToInt(ANewPIN)); 

  CheckStatus(ChangeCode(@iOldPin, 4, @iNewPin, 4));
end;

procedure ChangeUserPIN(const AOldPIN, ANewPIN: string);
var
  iOldPin, iNewPin: Integer;
begin
  iOldPin := StrToInt(AOldPIN);
  iNewPin := StrToInt(ANewPIN); 

  CheckStatus(ChangeCode(@iOldPin, 4, @iNewPin, 4));
end;

procedure ChangeUserPIN(const AOldPIN, ANewPIN: string);

  function StrToEndian(s: string): Integer;
  var
    i: Integer;
  begin
    Result := 0;
    for i := 1 to Length(s) do
      Result := Result shl 4 or (ord(s[i]) - ord('0'));
  end;

var
  iOldPin, iNewPin: Integer;
begin

  iOldPin := StrToEndian(AOldPIN);
  iNewPin := StrToEndian(ANewPIN); 

  CheckStatus(ChangeCode(@iOldPin, 4, @iNewPin, 4));
end;