function TOSFile.IsLastSystemCallSucceed: Boolean;
begin
  result :=
    GetLastError = ERROR_SUCCESS;
end;

function TOSFile.GetOSErrorString(const OSErrorCode: Integer): String;
begin
  result :=
    'OS Error: ' +
      SysErrorMessage(OSErrorCode) + ' (' + IntToStr(OSErrorCode) + ')';
end;

procedure TOSFile.IfOSErrorRaiseException;
var
  OSErrorException: EOSError;
begin
  if not IsLastSystemCallSucceed then
  begin
    OSErrorException := EOSError.Create(GetOSErrorString(GetLastError));
    OSErrorException.ErrorCode := GetLastError;
    raise OSErrorException;
  end;
end;