CRC16 File Calculatiing

Function CalcCRC16(const Buffer: array of byte; inCRC16: Word) : Word;
const
  Mask: Word = $A001;
var
  N, I: Integer;
  B: Byte;
begin
  for I := Low(Buffer) to High(Buffer) do
  begin
    B := Buffer[I];
    inCRC16 := inCRC16 xor B;
    for N := 1 to 8 do
     if (inCRC16 and 1) > 0 then
      inCRC16 := (inCRC16 shr 1) xor Mask
     else
      inCRC16 := (inCRC16 shr 1);
  end;
  Result := inCRC16;
end;

function FileCRC16(const FileName: string; var CRC16: Word; StartPos: Int64 = 0;
  Len: Int64 = 0): Boolean;
const
  csBuff_Size = 4096;
type
  TBuff = array[0..csBuff_Size - 1] of Byte;
var
  Handle: THandle;
  ReadCount: Integer;
  Size: Int64;
  Count: Int64;
  Buff: TBuff;
begin
  Handle := CreateFile(PChar(FileName), GENERIC_READ,
    FILE_SHARE_READ, nil, OPEN_EXISTING,
    FILE_ATTRIBUTE_NORMAL, 0);
  Result := Handle <> INVALID_HANDLE_VALUE;
  if Result then
  try
    Int64Rec(Size).Lo := GetFileSize(Handle, @Int64Rec(Size).Hi);
    if Size < StartPos + Len then
    begin
      Result := False;
      Exit;
    end;
    if Len > 0 then
      Count := Len
    else
      Count := Size - StartPos;
    CRC16 := not CRC16;
    SetFilePointer(Handle, Int64Rec(StartPos).Lo, @Int64Rec(StartPos).Hi, FILE_BEGIN);
    while Count > 0 do
    begin
      if Count > SizeOf(Buff) then
        ReadCount := SizeOf(Buff)
      else
        ReadCount := Count;
      ReadFile(Handle, Buff, ReadCount, LongWord(ReadCount), nil);
      CRC16 := CalcCRC16(Buff, CRC16);
      Dec(Count, ReadCount);
    end;
    CRC16 := not CRC16;
  finally
    CloseHandle(Handle);
  end;
end;

Beispiel :

procedure TForm1.Button1Click(Sender: TObject);
var
  CRC16: Word;
begin
  CRC16 := 0;
  if OpenDialog1.Execute then
   begin
    if FileCRC16(OpenDialog1.FileName, CRC16) then
    Label1.Caption := (IntToHex(CRC16, 4));
   end;
end;

Beispiel 2 :

procedure TForm1.Button2Click(Sender: TObject);
var
  s: String;
  buff: packed array of byte;
  i: Integer;
begin
  case RadioGroup1.ItemIndex of
   0: begin                     // FÜR DIE LANGE EINER DATEI
       s := Label1.Caption;
       SetLength(buff, Length(s));
       for i := 0 to (Length(s))-1 do buff[i] := Byte(Ord(s[i+1]));
       Label1.Caption := (IntToHex(CalcCRC16(buff, Word($0000)), 4));
      end;
   1: begin                    // FÜR DIE BYTES EINER DATEI	
       s := Label1.Caption;
       SetLength(buff, Length(s) div 2);
       for i := 0 to (Length(s) div 2)-1 do
        buff[i] := Byte(StrToInt('$'+s[i*2+1]+s[i*2+2]));
       Label1.Caption := (IntToHex(CalcCRC16(buff, Word($0000)), 4));
      end;
  end;
end;