C++¶

An I/O driver that is written in C or C++ looks similar to an I/O driver written in IEC except the start up- and shutdown phase. This difference is explained in this chapter.

An I/O driver in C/C++ must register its component interface at the component manager at start up of the runtime system (see Startup and Shutdown) in the ComponentEntry function. This is identical for all component written in C or C++.

After that, the typical start up sequence with the corresponding hooks is called by the component manager. In the CH_INIT2 hook, the I/O driver should detect its supported devices and should create one instance for each device with its local IoDrvCreate() function. After that, the I/O driver should register these instances at the I/O-manager or the Component-Manager. In the example code of the IoDrvTemplate, this looks like:

Ibase *s_pIBase = NULL;
  case CH_INIT2:
  {
  int iInstance = 0;
  RTS_RESULT Result;
  RTS_HANDLE hIoDrv = 0;
  /* Example: Create first instance */
  s_pIBase = (Ibase *)CAL_IoDrvCreate(hIoDrv, CLASSID_CioDrvTemplate, iInstance, &Result);
  CAL_IoMgrRegisterInstance(s_pIBase, NULL);

To unregister and delete the instance, you have to call the following sequence in CH_EXIT2:

case CH_EXIT2:
{
  /* Delete both instances */
  IcmpIoDrv *pI;
  CAL_IoMgrUnregisterInstance(s_pIBase);
  pI = (IcmpIoDrv *)s_pIBase->QueryInterface(s_pIBase, ITFID_IcmpIoDrv, NULL);
  s_pIBase->Release(s_pIBase);
  CAL_IoDrvDelete((RTS_HANDLE)pI, (RTS_HANDLE)pI);