var
stream: TMemoryStream;
CrcValue,OldCrcValue: DWORD;
exename: string;
WriteBuf: array[0..3] of Byte;
begin
CRCValue := $FFFFFFFF;           // 预设
WriteBuf[0]:= $00;
WriteBuf[1]:= $00;
WriteBuf[2]:= $00;
WriteBuf[3]:= $00;
exename:= application.ExeName;
stream:= TMemoryStream.Create;
stream.LoadFromFile(exename);     // 载入自身exe文件到内存流
stream.Position:= 220;            // 设定流的指针位置
stream.Read(OldCrcValue,4);       // 读取原来的CRC值
stream.Position:= 220;            // 设定流的指针位置,读取流时指针会自动相加
stream.Write(WriteBuf[0],4);      // 将储存CRC值处用00补充，以便计算CRC值是否改过
CalcCRC32(stream.Memory,stream.Size,CrcValue); // 计算CRC
CRCvalue := NOT CRCvalue;                       // 计算CRC
FreeAndNil(stream);
Edit1.Text:= IntToHex(OldCrcValue,8);
Edit2.Text:= IntToHex(CrcValue,8);
if CrcValue <> OldCrcValue then
    begin
      ShowMessage('文件已经被更改，程序退出！');
      Application.Terminate;
    end
else
    ShowMessage('文件校验正常！');
end;